diff --git a/packages/backend/src/core/activitypub/models/ApImageService.ts b/packages/backend/src/core/activitypub/models/ApImageService.ts
index 423044b985..383c77a177 100644
--- a/packages/backend/src/core/activitypub/models/ApImageService.ts
+++ b/packages/backend/src/core/activitypub/models/ApImageService.ts
@@ -18,7 +18,7 @@ import type { Config } from '@/config.js';
 import { IdentifiableError } from '@/misc/identifiable-error.js';
 import { ApResolverService } from '../ApResolverService.js';
 import { ApLoggerService } from '../ApLoggerService.js';
-import { isDocument, type IObject } from '../type.js';
+import { isDocument, type IObject, isApObject } from '../type.js';
 
 @Injectable()
 export class ApImageService {
diff --git a/packages/backend/src/core/activitypub/models/ApNoteService.ts b/packages/backend/src/core/activitypub/models/ApNoteService.ts
index 9fc6945edb..2995b1e764 100644
--- a/packages/backend/src/core/activitypub/models/ApNoteService.ts
+++ b/packages/backend/src/core/activitypub/models/ApNoteService.ts
@@ -25,7 +25,7 @@ import { UtilityService } from '@/core/UtilityService.js';
 import { bindThis } from '@/decorators.js';
 import { checkHttps } from '@/misc/check-https.js';
 import { IdentifiableError } from '@/misc/identifiable-error.js';
-import { getOneApId, getApId, getOneApHrefNullable, validPost, isEmoji, getApType } from '../type.js';
+import { getOneApId, getApId, getOneApHrefNullable, validPost, isEmoji, getApType, isApObject, isDocument, IApDocument } from '../type.js';
 import { ApLoggerService } from '../ApLoggerService.js';
 import { ApMfmService } from '../ApMfmService.js';
 import { ApDbResolverService } from '../ApDbResolverService.js';
@@ -270,6 +270,14 @@ export class ApNoteService {
 			if (file) files.push(file);
 		}
 
+		// Some software (Peertube) attaches a thumbnail under "icon" instead of "attachment"
+		const icon = getBestIcon(note);
+		if (icon) {
+			icon.sensitive ??= note.sensitive;
+			const file = await this.apImageService.resolveImage(actor, icon);
+			if (file) files.push(file);
+		}
+
 		// リプライ
 		const reply: MiNote | null = note.inReplyTo
 			? await this.resolveNote(note.inReplyTo, { resolver })
@@ -504,6 +512,14 @@ export class ApNoteService {
 			if (file) files.push(file);
 		}
 
+		// Some software (Peertube) attaches a thumbnail under "icon" instead of "attachment"
+		const icon = getBestIcon(note);
+		if (icon) {
+			icon.sensitive ??= note.sensitive;
+			const file = await this.apImageService.resolveImage(actor, icon);
+			if (file) files.push(file);
+		}
+
 		// リプライ
 		const reply: MiNote | null = note.inReplyTo
 			? await this.resolveNote(note.inReplyTo, { resolver })
@@ -719,3 +735,21 @@ export class ApNoteService {
 		}));
 	}
 }
+
+function getBestIcon(note: IObject): IObject | null {
+	const icons: IObject[] = toArray(note.icon);
+	if (icons.length < 2) {
+		return icons[0] ?? null;
+	}
+
+	return icons.reduce((best, i) => {
+		if (!isApObject(i)) return best;
+		if (!isDocument(i)) return best;
+		if (!best) return i;
+		if (!best.width || !best.height) return i;
+		if (!i.width || !i.height) return best;
+		if (i.width > best.width) return i;
+		if (i.height > best.height) return i;
+		return best;
+	}, null as IApDocument | null) ?? null;
+}
diff --git a/packages/backend/src/core/activitypub/type.ts b/packages/backend/src/core/activitypub/type.ts
index 4e0f131647..731a46c0d4 100644
--- a/packages/backend/src/core/activitypub/type.ts
+++ b/packages/backend/src/core/activitypub/type.ts
@@ -297,6 +297,8 @@ export const validDocumentTypes = ['Audio', 'Document', 'Image', 'Page', 'Video'
 
 export interface IApDocument extends IObject {
 	type: 'Audio' | 'Document' | 'Image' | 'Page' | 'Video';
+	width?: number;
+	height?: number;
 }
 
 export const isDocument = (object: IObject): object is IApDocument => {