diff --git a/packages/expo/src/client.ts b/packages/expo/src/client.ts
index cf9edaa5ae..0f957eb1e1 100644
--- a/packages/expo/src/client.ts
+++ b/packages/expo/src/client.ts
@@ -238,12 +238,39 @@ export function hasBetterAuthCookies(
 	return false;
 }
 
+/**
+ * Expo secure store does not support colons in the keys.
+ * This function replaces colons with underscores.
+ *
+ * @see https://github.com/better-auth/better-auth/issues/5426
+ *
+ * @param name cookie name to be saved in the storage
+ * @returns normalized cookie name
+ */
+export function normalizeCookieName(name: string) {
+	return name.replace(/:/g, "_");
+}
+
+export function storageAdapter(storage: {
+	getItem: (name: string) => string | null;
+	setItem: (name: string, value: string) => void;
+}) {
+	return {
+		getItem: (name: string) => {
+			return storage.getItem(normalizeCookieName(name));
+		},
+		setItem: (name: string, value: string) => {
+			return storage.setItem(normalizeCookieName(name), value);
+		},
+	};
+}
+
 export const expoClient = (opts: ExpoClientOptions) => {
 	let store: Store | null = null;
 	const storagePrefix = opts?.storagePrefix || "better-auth";
 	const cookieName = `${storagePrefix}_cookie`;
 	const localCacheName = `${storagePrefix}_session_data`;
-	const storage = opts?.storage;
+	const storage = storageAdapter(opts?.storage);
 	const isWeb = Platform.OS === "web";
 	const cookiePrefix = opts?.cookiePrefix || "better-auth";
 
diff --git a/packages/expo/src/expo.test.ts b/packages/expo/src/expo.test.ts
index dee41204ac..48459fe746 100644
--- a/packages/expo/src/expo.test.ts
+++ b/packages/expo/src/expo.test.ts
@@ -2,7 +2,7 @@ import { createAuthClient } from "better-auth/react";
 import Database from "better-sqlite3";
 import { beforeAll, afterAll, describe, expect, it, vi } from "vitest";
 import { expo } from ".";
-import { expoClient } from "./client";
+import { expoClient, storageAdapter } from "./client";
 import { betterAuth } from "better-auth";
 import { getMigrations } from "better-auth/db";
 import { oAuthProxy } from "better-auth/plugins";
@@ -325,4 +325,19 @@ describe("expo with cookieCache", async () => {
 
 		expect(hasBetterAuthCookies(customCookieHeader, "better-auth")).toBe(false);
 	});
+
+	it("should normalize colons in secure storage name via storage adapter", async () => {
+		const map = new Map<string, string>();
+		const storage = storageAdapter({
+			getItem(name) {
+				return map.get(name) || null;
+			},
+			setItem(name, value) {
+				map.set(name, value);
+			},
+		});
+		storage.setItem("better-auth:session_token", "123");
+		expect(map.has("better-auth_session_token")).toBe(true);
+		expect(map.has("better-auth:session_token")).toBe(false);
+	});
 });