diff --git a/.changeset/preview-url-respects-url-pattern.md b/.changeset/preview-url-respects-url-pattern.md
new file mode 100644
index 0000000000..9616f94078
--- /dev/null
+++ b/.changeset/preview-url-respects-url-pattern.md
@@ -0,0 +1,5 @@
+---
+"emdash": patch
+---
+
+Fixes preview links 404ing on sites with a custom collection `url_pattern`. The content Preview button now resolves the collection's `url_pattern` (the same route the sitemap and "View published" links use) instead of the hard-coded `/{collection}/{id}`, falling back to `/{collection}/{id}` only when no pattern is configured. An explicit `pathPattern` or `EMDASH_PREVIEW_PATH_PATTERN` still takes precedence.
diff --git a/packages/core/src/astro/routes/api/content/[collection]/[id]/preview-url.ts b/packages/core/src/astro/routes/api/content/[collection]/[id]/preview-url.ts
index 71e43dad31..a2df8964ae 100644
--- a/packages/core/src/astro/routes/api/content/[collection]/[id]/preview-url.ts
+++ b/packages/core/src/astro/routes/api/content/[collection]/[id]/preview-url.ts
@@ -6,9 +6,18 @@
  * Request body:
  * {
  *   expiresIn?: string | number;  // Default: "1h"
- *   pathPattern?: string;         // Default: "/{collection}/{id}" (or EMDASH_PREVIEW_PATH_PATTERN)
+ *   pathPattern?: string;         // Overrides the resolved default (see below)
  * }
  *
+ * Path resolution precedence (highest first):
+ *   1. `pathPattern` in the request body (per-call override)
+ *   2. `EMDASH_PREVIEW_PATH_PATTERN` env (project-wide override)
+ *   3. the collection's configured `url_pattern` — so preview links match the
+ *      same routes the sitemap and "View published" links already use (incl.
+ *      custom permalinks like `/blog/{slug}`), resolved via the shared
+ *      `interpolateUrlPattern` + `localizePath` helpers.
+ *   4. the generic `/{collection}/{id}` fallback.
+ *
  * Response:
  * {
  *   url: string;      // The preview URL with token
@@ -23,9 +32,11 @@ import { apiError, apiSuccess, handleError, unwrapResult } from "#api/error.js";
 import { parseOptionalBody, isParseError } from "#api/parse.js";
 import { contentPreviewUrlBody } from "#api/schemas.js";
 import { resolveSecretsCached } from "#config/secrets.js";
-import { getPreviewUrl } from "#preview/index.js";
+import { buildPreviewUrl, generatePreviewToken, getPreviewUrl } from "#preview/index.js";
+import { getCollectionInfoWithDb } from "#schema/query.js";
 
 import { getI18nConfig } from "../../../../../../i18n/config.js";
+import { interpolateUrlPattern, localizePath } from "../../../../../../i18n/resolve.js";
 
 export const prerender = false;
 
@@ -49,12 +60,14 @@ export const POST: APIRoute = async ({ params, request, locals }) => {
 	const { previewSecret } = await resolveSecretsCached(emdash.db);
 
 	// Verify the content exists. The fetched item also yields the entry's
-	// locale, used below to resolve the `{locale}` placeholder.
+	// locale and slug, used below to resolve the public path.
 	let entryLocale: string | null = null;
+	let entrySlug: string | null = null;
 	if (emdash?.handleContentGet) {
 		const result = await emdash.handleContentGet(collection, id);
 		if (!result.success) return unwrapResult(result);
 		entryLocale = result.data?.item?.locale ?? null;
+		entrySlug = result.data?.item?.slug ?? null;
 	}
 
 	// Parse request body
@@ -62,15 +75,14 @@ export const POST: APIRoute = async ({ params, request, locals }) => {
 	if (isParseError(body)) return body;
 
 	const expiresIn = body.expiresIn || "1h";
-	// Allow a project-wide default `pathPattern` so the admin's "View on site"
-	// link can match the site's actual route shape without each call having
-	// to override the default `/{collection}/{id}`.
-	const defaultPathPattern = import.meta.env.EMDASH_PREVIEW_PATH_PATTERN || "/{collection}/{id}";
-	const pathPattern = body.pathPattern || defaultPathPattern;
-
-	// Resolve the locale segment substituted for `{locale}`: empty when the
-	// entry is in the default locale and `prefixDefaultLocale` is `false`,
-	// the entry's own locale otherwise.
+	// A project-wide default `pathPattern` (body or env) always wins so callers
+	// can force a specific shape. When neither is set we resolve the
+	// collection's own `url_pattern` below.
+	const explicitPattern = body.pathPattern || import.meta.env.EMDASH_PREVIEW_PATH_PATTERN || null;
+
+	// Resolve the locale segment substituted for the `{locale}` placeholder in
+	// an explicit pattern: empty when the entry is in the default locale and
+	// `prefixDefaultLocale` is `false`, the entry's own locale otherwise.
 	const i18n = getI18nConfig();
 	let localeSegment = "";
 	if (entryLocale && i18n) {
@@ -85,12 +97,40 @@ export const POST: APIRoute = async ({ params, request, locals }) => {
 	const expiresAt = Math.floor(Date.now() / 1000) + expiresInSeconds;
 
 	try {
+		// No explicit override: reuse the collection's `url_pattern` so the
+		// preview link points at the same route the sitemap and "View
+		// published" links already use (custom permalinks like `/blog/{slug}`).
+		// Without this the generic `/{collection}/{id}` fallback 404s on any
+		// site whose content isn't served at that path.
+		if (!explicitPattern) {
+			const collectionInfo = await getCollectionInfoWithDb(emdash.db, collection);
+			if (collectionInfo?.urlPattern) {
+				const path = interpolateUrlPattern({
+					pattern: collectionInfo.urlPattern,
+					collection,
+					slug: entrySlug || id,
+					id,
+				});
+				// `localizePath` returns null when the entry's locale isn't in the
+				// configured i18n list; fall back to the un-prefixed path so we
+				// still hand back a usable preview link rather than failing.
+				const localized = await localizePath(path, entryLocale ?? "");
+				const token = await generatePreviewToken({
+					contentId: `${collection}:${id}`,
+					expiresIn,
+					secret: previewSecret,
+				});
+				const url = buildPreviewUrl({ path: localized ?? path, token });
+				return apiSuccess({ url, expiresAt });
+			}
+		}
+
 		const url = await getPreviewUrl({
 			collection,
 			id,
 			secret: previewSecret,
 			expiresIn,
-			pathPattern,
+			pathPattern: explicitPattern || "/{collection}/{id}",
 			locale: localeSegment,
 		});
 
diff --git a/packages/core/tests/unit/api/preview-url-route.test.ts b/packages/core/tests/unit/api/preview-url-route.test.ts
new file mode 100644
index 0000000000..f89e6276aa
--- /dev/null
+++ b/packages/core/tests/unit/api/preview-url-route.test.ts
@@ -0,0 +1,133 @@
+import { Role } from "@emdash-cms/auth";
+import type { Kysely } from "kysely";
+import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
+
+import { handleContentCreate, handleContentGet } from "../../../src/api/index.js";
+import { POST as previewUrl } from "../../../src/astro/routes/api/content/[collection]/[id]/preview-url.js";
+import type { Database } from "../../../src/database/types.js";
+import { setI18nConfig } from "../../../src/i18n/config.js";
+import { _resetAstroI18nCacheForTests } from "../../../src/i18n/resolve.js";
+import { SchemaRegistry } from "../../../src/schema/registry.js";
+import { setupTestDatabaseWithCollections, teardownTestDatabase } from "../../utils/test-db.js";
+
+/**
+ * Regression: the preview-url endpoint used a hard-coded `/{collection}/{id}`
+ * default, ignoring the collection's configured `url_pattern`. On any site
+ * whose content is served at a custom permalink (e.g. `/blog/{slug}`) the
+ * admin "Preview" button produced a link that 404'd. The sitemap and
+ * "View published" links already resolve the same `url_pattern`; the preview
+ * link must too. See discussion #1525 / PR #1526.
+ */
+describe("preview-url route — respects collection url_pattern", () => {
+	let db: Kysely<Database>;
+
+	const call = async (collection: string, id: string, body: Record<string, unknown> = {}) => {
+		const request = new Request(
+			`http://localhost/_emdash/api/content/${collection}/${id}/preview-url`,
+			{
+				method: "POST",
+				headers: { "Content-Type": "application/json" },
+				body: JSON.stringify(body),
+			},
+		);
+		const response = await previewUrl({
+			params: { collection, id },
+			request,
+			locals: {
+				emdash: {
+					db,
+					handleContentGet: (c: string, i: string) => handleContentGet(db, c, i),
+				},
+				user: { id: "u1", role: Role.ADMIN },
+			},
+		} as unknown as Parameters<typeof previewUrl>[0]);
+		return response;
+	};
+
+	beforeEach(async () => {
+		db = await setupTestDatabaseWithCollections();
+	});
+
+	afterEach(async () => {
+		vi.unstubAllEnvs();
+		setI18nConfig(null);
+		_resetAstroI18nCacheForTests();
+		await teardownTestDatabase(db);
+	});
+
+	it("resolves the configured url_pattern into the preview link", async () => {
+		await new SchemaRegistry(db).updateCollection("post", { urlPattern: "/blog/{slug}" });
+		const created = await handleContentCreate(db, "post", {
+			data: { title: "Hello World" },
+		});
+		const id = created.data!.item.id;
+
+		const response = await call("post", id);
+		expect(response.status).toBe(200);
+		const { url } = (await response.json()).data as { url: string };
+
+		expect(url.startsWith("/blog/hello-world?_preview=")).toBe(true);
+		// The generic collection/id fallback must NOT leak through.
+		expect(url.startsWith("/post/")).toBe(false);
+	});
+
+	it("falls back to /{collection}/{id} when no url_pattern is configured", async () => {
+		const created = await handleContentCreate(db, "post", {
+			data: { title: "No Pattern" },
+		});
+		const id = created.data!.item.id;
+
+		const response = await call("post", id);
+		expect(response.status).toBe(200);
+		const { url } = (await response.json()).data as { url: string };
+
+		expect(url.startsWith(`/post/${id}?_preview=`)).toBe(true);
+	});
+
+	it("lets an explicit pathPattern override the url_pattern", async () => {
+		await new SchemaRegistry(db).updateCollection("post", { urlPattern: "/blog/{slug}" });
+		const created = await handleContentCreate(db, "post", {
+			data: { title: "Override Me" },
+		});
+		const id = created.data!.item.id;
+
+		const response = await call("post", id, { pathPattern: "/custom/{id}" });
+		expect(response.status).toBe(200);
+		const { url } = (await response.json()).data as { url: string };
+
+		expect(url.startsWith(`/custom/${id}?_preview=`)).toBe(true);
+	});
+
+	it("lets the EMDASH_PREVIEW_PATH_PATTERN env override win over the url_pattern", async () => {
+		vi.stubEnv("EMDASH_PREVIEW_PATH_PATTERN", "/env/{id}");
+		await new SchemaRegistry(db).updateCollection("post", { urlPattern: "/blog/{slug}" });
+		const created = await handleContentCreate(db, "post", {
+			data: { title: "Env Wins" },
+		});
+		const id = created.data!.item.id;
+
+		const response = await call("post", id);
+		expect(response.status).toBe(200);
+		const { url } = (await response.json()).data as { url: string };
+
+		expect(url.startsWith(`/env/${id}?_preview=`)).toBe(true);
+		expect(url.startsWith("/blog/")).toBe(false);
+	});
+
+	it("prefixes the locale segment for a non-default-locale entry", async () => {
+		setI18nConfig({ defaultLocale: "en", locales: ["en", "de"], prefixDefaultLocale: false });
+		_resetAstroI18nCacheForTests();
+		await new SchemaRegistry(db).updateCollection("post", { urlPattern: "/blog/{slug}" });
+		const created = await handleContentCreate(db, "post", {
+			data: { title: "Hallo Welt" },
+			locale: "de",
+		});
+		const id = created.data!.item.id;
+
+		const response = await call("post", id);
+		expect(response.status).toBe(200);
+		const { url } = (await response.json()).data as { url: string };
+
+		expect(url.startsWith("/de/blog/hallo-welt?_preview=")).toBe(true);
+	});
+});