diff --git a/app/(app)/lish/createPub/createPublication.ts b/app/(app)/lish/createPub/createPublication.ts
index 5adcc7ee..c553988c 100644
--- a/app/(app)/lish/createPub/createPublication.ts
+++ b/app/(app)/lish/createPub/createPublication.ts
@@ -13,6 +13,7 @@ import { Vercel } from "@vercel/sdk";
 import { isProductionDomain } from "src/utils/isProductionDeployment";
 import { string } from "zod";
 import { getPublicationType } from "src/utils/collectionHelpers";
+import { resizePublicationIcon } from "src/utils/resizePublicationIcon";
 import { PubThemeDefaultsRGB } from "components/ThemeManager/themeDefaults";
 
 const VERCEL_TOKEN = process.env.VERCEL_TOKEN;
@@ -81,11 +82,10 @@ export async function createPublication({
 
   // Upload the icon if provided
   if (iconFile && iconFile.size > 0) {
-    const buffer = await iconFile.arrayBuffer();
-    const uploadResult = await agent.com.atproto.repo.uploadBlob(
-      new Uint8Array(buffer),
-      { encoding: iconFile.type },
-    );
+    const { data, encoding } = await resizePublicationIcon(iconFile);
+    const uploadResult = await agent.com.atproto.repo.uploadBlob(data, {
+      encoding,
+    });
     iconBlob = uploadResult.data.blob;
   }
 
diff --git a/app/(app)/lish/createPub/updatePublication.ts b/app/(app)/lish/createPub/updatePublication.ts
index 4eaf4874..7abec1d7 100644
--- a/app/(app)/lish/createPub/updatePublication.ts
+++ b/app/(app)/lish/createPub/updatePublication.ts
@@ -16,6 +16,7 @@ import {
   type NormalizedPublication,
 } from "src/utils/normalizeRecords";
 import { getPublicationType } from "src/utils/collectionHelpers";
+import { resizePublicationIcon } from "src/utils/resizePublicationIcon";
 
 type UpdatePublicationResult =
   | { success: true; publication: any }
@@ -263,11 +264,10 @@ export async function updatePublication({
       // Upload icon if provided
       let iconBlob = normalizedPub?.icon;
       if (iconFile && iconFile.size > 0) {
-        const buffer = await iconFile.arrayBuffer();
-        const uploadResult = await agent.com.atproto.repo.uploadBlob(
-          new Uint8Array(buffer),
-          { encoding: iconFile.type },
-        );
+        const { data, encoding } = await resizePublicationIcon(iconFile);
+        const uploadResult = await agent.com.atproto.repo.uploadBlob(data, {
+          encoding,
+        });
         if (uploadResult.data.blob) {
           iconBlob = uploadResult.data.blob;
         }
diff --git a/src/utils/resizePublicationIcon.ts b/src/utils/resizePublicationIcon.ts
new file mode 100644
index 00000000..1fb6d94e
--- /dev/null
+++ b/src/utils/resizePublicationIcon.ts
@@ -0,0 +1,29 @@
+import sharp from "sharp";
+
+// Publication icons are rendered at most at 48px (the `w-12 h-12` PubIcon
+// variant / 40px header). We keep a 3x buffer for high-DPI ("retina") displays,
+// so there's no point uploading anything larger than this to the PDS.
+const MAX_ICON_SIZE = 144;
+
+// Scale an uploaded icon down to the size it's actually displayed at and
+// re-encode it as WebP. Uses `fit: "inside"` so aspect ratio is preserved (the
+// square crop happens via CSS at display time) and `withoutEnlargement` so
+// small icons aren't upscaled. Falls back to the original bytes if sharp can't
+// process the input (e.g. an unsupported format).
+export async function resizePublicationIcon(
+  file: File,
+): Promise<{ data: Uint8Array; encoding: string }> {
+  const original = new Uint8Array(await file.arrayBuffer());
+  try {
+    const resized = await sharp(Buffer.from(original))
+      .resize(MAX_ICON_SIZE, MAX_ICON_SIZE, {
+        fit: "inside",
+        withoutEnlargement: true,
+      })
+      .webp({ quality: 90 })
+      .toBuffer();
+    return { data: new Uint8Array(resized), encoding: "image/webp" };
+  } catch {
+    return { data: original, encoding: file.type };
+  }
+}