diff --git a/src/data/mqtt.ts b/src/data/mqtt.ts
index d91b32ce13..d00f9f2415 100644
--- a/src/data/mqtt.ts
+++ b/src/data/mqtt.ts
@@ -7,6 +7,31 @@ export interface MQTTMessage {
   retain: number;
 }
 
+export interface MQTTTopicDebugInfo {
+  topic: string;
+  messages: MQTTMessage[];
+}
+
+export interface MQTTDiscoveryDebugInfo {
+  topic: string;
+  payload: string;
+}
+
+export interface MQTTEntityDebugInfo {
+  entity_id: string;
+  discovery_data: MQTTDiscoveryDebugInfo;
+  subscriptions: MQTTTopicDebugInfo[];
+}
+
+export interface MQTTTriggerDebugInfo {
+  discovery_data: MQTTDiscoveryDebugInfo;
+}
+
+export interface MQTTDeviceDebugInfo {
+  entities: MQTTEntityDebugInfo[];
+  triggers: MQTTTriggerDebugInfo[];
+}
+
 export const subscribeMQTTTopic = (
   hass: HomeAssistant,
   topic: string,
@@ -26,3 +51,12 @@ export const removeMQTTDeviceEntry = (
     type: "mqtt/device/remove",
     device_id: deviceId,
   });
+
+export const fetchMQTTDebugInfo = (
+  hass: HomeAssistant,
+  deviceId: string
+): Promise<MQTTDeviceDebugInfo> =>
+  hass.callWS<MQTTDeviceDebugInfo>({
+    type: "mqtt/device/debug_info",
+    device_id: deviceId,
+  });
diff --git a/src/dialogs/mqtt-device-debug-info-dialog/dialog-mqtt-device-debug-info.ts b/src/dialogs/mqtt-device-debug-info-dialog/dialog-mqtt-device-debug-info.ts
new file mode 100644
index 0000000000..80ce1a52ef
--- /dev/null
+++ b/src/dialogs/mqtt-device-debug-info-dialog/dialog-mqtt-device-debug-info.ts
@@ -0,0 +1,215 @@
+import {
+  LitElement,
+  css,
+  html,
+  CSSResult,
+  TemplateResult,
+  customElement,
+  property,
+} from "lit-element";
+import "../../components/ha-dialog";
+import "../../components/ha-switch";
+import { computeDeviceName } from "../../data/device_registry";
+import { computeStateName } from "../../common/entity/compute_state_name";
+import { haStyleDialog } from "../../resources/styles";
+import type { HaSwitch } from "../../components/ha-switch";
+import { HomeAssistant } from "../../types";
+import { MQTTDeviceDebugInfoDialogParams } from "./show-dialog-mqtt-device-debug-info";
+import { MQTTDeviceDebugInfo, fetchMQTTDebugInfo } from "../../data/mqtt";
+import "./mqtt-messages";
+import "./mqtt-discovery-payload";
+
+@customElement("dialog-mqtt-device-debug-info")
+class DialogMQTTDeviceDebugInfo extends LitElement {
+  public hass!: HomeAssistant;
+
+  @property() private _params?: MQTTDeviceDebugInfoDialogParams;
+
+  @property() private _debugInfo?: MQTTDeviceDebugInfo;
+
+  @property() private _showAsYaml = true;
+
+  @property() private _showDeserialized = true;
+
+  public async showDialog(
+    params: MQTTDeviceDebugInfoDialogParams
+  ): Promise<void> {
+    this._params = params;
+    fetchMQTTDebugInfo(this.hass, params.device.id).then((results) => {
+      this._debugInfo = results;
+    });
+  }
+
+  protected render(): TemplateResult {
+    if (!this._params || !this._debugInfo) {
+      return html``;
+    }
+
+    return html`
+      <ha-dialog
+        open
+        @closing=${this._close}
+        .heading="${this.hass!.localize(
+          "ui.dialogs.mqtt_device_debug_info.title",
+          "device",
+          computeDeviceName(this._params.device, this.hass)
+        )}"
+      >
+        <h4>
+          ${this.hass!.localize(
+            "ui.dialogs.mqtt_device_debug_info.payload_display"
+          )}
+        </h4>
+        <ha-switch
+          .checked=${this._showDeserialized}
+          @change=${this._showDeserializedChanged}
+        >
+          ${this.hass!.localize(
+            "ui.dialogs.mqtt_device_debug_info.deserialize"
+          )}
+        </ha-switch>
+        <ha-switch
+          .checked=${this._showAsYaml}
+          @change=${this._showAsYamlChanged}
+        >
+          ${this.hass!.localize(
+            "ui.dialogs.mqtt_device_debug_info.show_as_yaml"
+          )}
+        </ha-switch>
+        <h4>
+          ${this.hass!.localize("ui.dialogs.mqtt_device_debug_info.entities")}
+        </h4>
+        <ul>
+          ${this._debugInfo.entities.length
+            ? this._renderEntities()
+            : html`
+                ${this.hass!.localize(
+                  "ui.dialogs.mqtt_device_debug_info.no_entities"
+                )}
+              `}
+        </ul>
+        <h4>
+          ${this.hass!.localize("ui.dialogs.mqtt_device_debug_info.triggers")}
+        </h4>
+        <ul>
+          ${this._debugInfo.triggers.length
+            ? this._renderTriggers()
+            : html`
+                ${this.hass!.localize(
+                  "ui.dialogs.mqtt_device_debug_info.no_triggers"
+                )}
+              `}
+        </ul>
+        <mwc-button slot="primaryAction" @click=${this._close}>
+          ${this.hass!.localize("ui.dialogs.generic.close")}
+        </mwc-button>
+      </ha-dialog>
+    `;
+  }
+
+  private _close(): void {
+    this._params = undefined;
+    this._debugInfo = undefined;
+  }
+
+  private _showAsYamlChanged(ev: Event): void {
+    this._showAsYaml = (ev.target as HaSwitch).checked;
+  }
+
+  private _showDeserializedChanged(ev: Event): void {
+    this._showDeserialized = (ev.target as HaSwitch).checked;
+  }
+
+  private _renderEntities(): TemplateResult {
+    return html`
+      ${this._debugInfo!.entities.map(
+        (entity) => html`
+          <li>
+            '${computeStateName(this.hass.states[entity.entity_id])}'
+            (<code>${entity.entity_id}</code>)
+            <br />MQTT discovery data:
+            <ul>
+              <li>
+                Topic:
+                <code>${entity.discovery_data.topic}</code>
+              </li>
+              <li>
+                <mqtt-discovery-payload
+                  .hass=${this.hass}
+                  .payload=${entity.discovery_data.payload}
+                  .showAsYaml=${this._showAsYaml}
+                  .summary=${"Payload"}
+                >
+                </mqtt-discovery-payload>
+              </li>
+            </ul>
+            Subscribed topics:
+            <ul>
+              ${entity.subscriptions.map(
+                (topic) => html`
+                  <li>
+                    <code>${topic.topic}</code>
+                    <mqtt-messages
+                      .hass=${this.hass}
+                      .messages=${topic.messages}
+                      .showDeserialized=${this._showDeserialized}
+                      .showAsYaml=${this._showAsYaml}
+                      .subscribedTopic=${topic.topic}
+                      .summary=${this.hass!.localize(
+                        "ui.dialogs.mqtt_device_debug_info.recent_messages",
+                        "n",
+                        topic.messages.length
+                      )}
+                    >
+                    </mqtt-messages>
+                  </li>
+                `
+              )}
+            </ul>
+          </li>
+        `
+      )}
+    `;
+  }
+
+  private _renderTriggers(): TemplateResult {
+    return html`
+      ${this._debugInfo!.triggers.map(
+        (trigger) => html`
+          <li>
+            Discovery topic:
+            <code>${trigger.discovery_data.topic}</code>
+            <mqtt-discovery-payload
+              .hass=${this.hass}
+              .payload=${trigger.discovery_data.payload}
+              .showAsYaml=${this._showAsYaml}
+              .summary="Discovery payload"
+            >
+            </mqtt-discovery-payload>
+          </li>
+        `
+      )}
+    `;
+  }
+
+  static get styles(): CSSResult[] {
+    return [
+      haStyleDialog,
+      css`
+        ha-dialog {
+          --mdc-dialog-max-width: 95%;
+          --mdc-dialog-min-width: 640px;
+        }
+        ha-switch {
+          margin: 16px;
+        }
+      `,
+    ];
+  }
+}
+
+declare global {
+  interface HTMLElementTagNameMap {
+    "dialog-mqtt-device-debug-info": DialogMQTTDeviceDebugInfo;
+  }
+}
diff --git a/src/dialogs/mqtt-device-debug-info-dialog/mqtt-discovery-payload.ts b/src/dialogs/mqtt-device-debug-info-dialog/mqtt-discovery-payload.ts
new file mode 100644
index 0000000000..b000f5499a
--- /dev/null
+++ b/src/dialogs/mqtt-device-debug-info-dialog/mqtt-discovery-payload.ts
@@ -0,0 +1,49 @@
+import {
+  LitElement,
+  html,
+  TemplateResult,
+  customElement,
+  property,
+} from "lit-element";
+import { safeDump } from "js-yaml";
+
+@customElement("mqtt-discovery-payload")
+class MQTTDiscoveryPayload extends LitElement {
+  @property() public payload!: object;
+
+  @property() public showAsYaml = false;
+
+  @property() public summary!: string;
+
+  @property() private _open = false;
+
+  protected render(): TemplateResult {
+    return html`
+      <details @toggle=${this._handleToggle}>
+        <summary>
+          ${this.summary}
+        </summary>
+        ${this._open ? this._renderPayload() : ""}
+      </details>
+    `;
+  }
+
+  private _renderPayload(): TemplateResult {
+    const payload = this.payload;
+    return html`
+      ${this.showAsYaml
+        ? html` <pre>${safeDump(payload)}</pre> `
+        : html` <pre>${JSON.stringify(payload, null, 2)}</pre> `}
+    `;
+  }
+
+  private _handleToggle(ev) {
+    this._open = ev.target.open;
+  }
+}
+
+declare global {
+  interface HTMLElementTagNameMap {
+    "mqtt-discovery-payload": MQTTDiscoveryPayload;
+  }
+}
diff --git a/src/dialogs/mqtt-device-debug-info-dialog/mqtt-messages.ts b/src/dialogs/mqtt-device-debug-info-dialog/mqtt-messages.ts
new file mode 100644
index 0000000000..c3f3b799ef
--- /dev/null
+++ b/src/dialogs/mqtt-device-debug-info-dialog/mqtt-messages.ts
@@ -0,0 +1,130 @@
+import {
+  LitElement,
+  html,
+  TemplateResult,
+  customElement,
+  property,
+} from "lit-element";
+import { safeDump } from "js-yaml";
+import { MQTTMessage } from "../../data/mqtt";
+
+@customElement("mqtt-messages")
+class MQTTMessages extends LitElement {
+  @property() public messages!: MQTTMessage[];
+
+  @property() public showAsYaml = false;
+
+  @property() public showDeserialized = false;
+
+  @property() public subscribedTopic!: string;
+
+  @property() public summary!: string;
+
+  @property() private _open = false;
+
+  @property() private _payloadsJson = new WeakMap();
+
+  @property() private _showTopic = false;
+
+  protected firstUpdated(): void {
+    this.messages.forEach((message) => {
+      // If any message's topic differs from the subscribed topic, show topics + payload
+      if (this.subscribedTopic !== message.topic) {
+        this._showTopic = true;
+      }
+    });
+  }
+
+  protected render(): TemplateResult {
+    return html`
+      <details @toggle=${this._handleToggle}>
+        <summary>
+          ${this.summary}
+        </summary>
+        ${this._open
+          ? html`
+              <ul>
+                ${this.messages.map(
+                  (message) => html`
+                    <li>
+                      ${this._renderSingleMessage(message)}
+                    </li>
+                  `
+                )}
+              </ul>
+            `
+          : ""}
+      </details>
+    `;
+  }
+
+  private _renderSingleMessage(message): TemplateResult {
+    const topic = message.topic;
+    return this._showTopic
+      ? html`
+          <ul>
+            <li>
+              Topic: ${topic}
+            </li>
+            <li>
+              Payload: ${this._renderSinglePayload(message)}
+            </li>
+          </ul>
+        `
+      : this._renderSinglePayload(message);
+  }
+
+  private _renderSinglePayload(message): TemplateResult {
+    let json;
+
+    if (this.showDeserialized) {
+      if (!this._payloadsJson.has(message)) {
+        json = this._tryParseJson(message.payload);
+        this._payloadsJson.set(message, json);
+      } else {
+        json = this._payloadsJson.get(message);
+      }
+    }
+
+    return json
+      ? html`
+          ${this.showAsYaml
+            ? html` <pre>${safeDump(json)}</pre> `
+            : html` <pre>${JSON.stringify(json, null, 2)}</pre> `}
+        `
+      : html` <code>${message.payload}</code> `;
+  }
+
+  private _tryParseJson(payload) {
+    let jsonPayload = null;
+    let o = payload;
+
+    // If the payload is a string, determine if the payload is valid JSON and if it
+    // is, assign the object representation to this._payloadJson.
+    if (typeof payload === "string") {
+      try {
+        o = JSON.parse(payload);
+      } catch (e) {
+        o = null;
+      }
+    }
+    // Handle non-exception-throwing cases:
+    // Neither JSON.parse(false) or JSON.parse(1234) throw errors, hence the type-checking,
+    // but... JSON.parse(null) returns null, and typeof null === "object",
+    // so we must check for that, too. Thankfully, null is falsey, so this suffices:
+    if (o && typeof o === "object") {
+      jsonPayload = o;
+    }
+    return jsonPayload;
+  }
+
+  private _handleToggle(ev) {
+    this._open = ev.target.open;
+  }
+}
+
+declare global {
+  interface HTMLElementTagNameMap {
+    "mqtt-messages": MQTTMessages;
+  }
+}
diff --git a/src/dialogs/mqtt-device-debug-info-dialog/show-dialog-mqtt-device-debug-info.ts b/src/dialogs/mqtt-device-debug-info-dialog/show-dialog-mqtt-device-debug-info.ts
new file mode 100644
index 0000000000..92fe6554cc
--- /dev/null
+++ b/src/dialogs/mqtt-device-debug-info-dialog/show-dialog-mqtt-device-debug-info.ts
@@ -0,0 +1,22 @@
+import { fireEvent } from "../../common/dom/fire_event";
+import { DeviceRegistryEntry } from "../../data/device_registry";
+
+export interface MQTTDeviceDebugInfoDialogParams {
+  device: DeviceRegistryEntry;
+}
+
+export const loadMQTTDeviceDebugInfoDialog = () =>
+  import(
+    /* webpackChunkName: "dialog-mqtt-device-debug-info" */ "./dialog-mqtt-device-debug-info"
+  );
+
+export const showMQTTDeviceDebugInfoDialog = (
+  element: HTMLElement,
+  mqttDeviceInfoParams: MQTTDeviceDebugInfoDialogParams
+): void => {
+  fireEvent(element, "show-dialog", {
+    dialogTag: "dialog-mqtt-device-debug-info",
+    dialogImport: loadMQTTDeviceDebugInfoDialog,
+    dialogParams: mqttDeviceInfoParams,
+  });
+};
diff --git a/src/panels/config/devices/device-detail/ha-device-card-mqtt.ts b/src/panels/config/devices/device-detail/ha-device-card-mqtt.ts
index cce083ac15..c2d1e9e824 100644
--- a/src/panels/config/devices/device-detail/ha-device-card-mqtt.ts
+++ b/src/panels/config/devices/device-detail/ha-device-card-mqtt.ts
@@ -1,16 +1,17 @@
-import {
-  CSSResult,
-  customElement,
-  html,
-  LitElement,
-  property,
-  TemplateResult,
-} from "lit-element";
 import { DeviceRegistryEntry } from "../../../../data/device_registry";
 import { removeMQTTDeviceEntry } from "../../../../data/mqtt";
+import {
+  LitElement,
+  html,
+  customElement,
+  property,
+  TemplateResult,
+  CSSResult,
+} from "lit-element";
 import { showConfirmationDialog } from "../../../../dialogs/generic/show-dialog-box";
-import { haStyle } from "../../../../resources/styles";
+import { showMQTTDeviceDebugInfoDialog } from "../../../../dialogs/mqtt-device-debug-info-dialog/show-dialog-mqtt-device-debug-info";
 import { HomeAssistant } from "../../../../types";
+import { haStyle } from "../../../../resources/styles";
 
 @customElement("ha-device-card-mqtt")
 export class HaDeviceCardMqtt extends LitElement {
@@ -20,6 +21,9 @@ export class HaDeviceCardMqtt extends LitElement {
 
   protected render(): TemplateResult {
     return html`
+      <mwc-button @click=${this._showDebugInfo}>
+        MQTT Info
+      </mwc-button>
       <mwc-button class="warning" @click="${this._confirmDeleteEntry}">
         ${this.hass.localize("ui.panel.config.devices.delete")}
       </mwc-button>
@@ -38,6 +42,11 @@ export class HaDeviceCardMqtt extends LitElement {
     await removeMQTTDeviceEntry(this.hass!, this.device.id);
   }
 
+  private async _showDebugInfo(): Promise<void> {
+    const device = this.device;
+    await showMQTTDeviceDebugInfoDialog(this, { device });
+  }
+
   static get styles(): CSSResult {
     return haStyle;
   }
diff --git a/src/translations/en.json b/src/translations/en.json
index 9f9df680cc..26ddad1a5e 100755
--- a/src/translations/en.json
+++ b/src/translations/en.json
@@ -456,6 +456,17 @@
       },
       "domain_toggler": {
         "title": "Toggle Domains"
+      },
+      "mqtt_device_debug_info": {
+        "title": "{device} debug info",
+        "deserialize": "Attempt to parse MQTT messages as JSON",
+        "entities": "Entities",
+        "no_entities": "No entities",
+        "no_triggers": "No triggers",
+        "payload_display": "Payload display",
+        "recent_messages": "{n} most recently received message(s)",
+        "show_as_yaml": "Show as YAML",
+        "triggers": "Triggers"
       }
     },
     "duration": {