diff --git a/packages/runtime/src/index.ts b/packages/runtime/src/index.ts
index f15bf13192..d420d5549b 100644
--- a/packages/runtime/src/index.ts
+++ b/packages/runtime/src/index.ts
@@ -121,10 +121,20 @@ const plugin: NetlifyPlugin = {
 
       if (userDefinedNextAuthUrl) {
         console.log(
-          `NextAuth package detected, NEXTAUTH_URL environment variable set by user to ${userDefinedNextAuthUrl}`,
+          `NextAuth package detected, NEXTAUTH_URL environment variable set by user in next.config.js to ${userDefinedNextAuthUrl}`,
         )
+      } else if (process.env.NEXTAUTH_URL) {
+        // When the value is specified in the netlify.toml or the Netlify UI (will be evaluated in this order)
+        const nextAuthUrl = `${process.env.NEXTAUTH_URL}${basePath}`
+
+        console.log(
+          `NextAuth package detected, NEXTAUTH_URL environment variable set by user in Netlify configuration to ${nextAuthUrl}`,
+        )
+        config.config.env.NEXTAUTH_URL = nextAuthUrl
+
+        await updateRequiredServerFiles(publish, config)
       } else {
-        const nextAuthUrl = `${process.env.URL}${basePath}`
+        const nextAuthUrl = `${process.env.DEPLOY_PRIME_URL}${basePath}`
 
         console.log(`NextAuth package detected, setting NEXTAUTH_URL environment variable to ${nextAuthUrl}`)
         config.config.env.NEXTAUTH_URL = nextAuthUrl
diff --git a/test/index.js b/test/index.js
index 1a92b6d487..37ebeed60b 100644
--- a/test/index.js
+++ b/test/index.js
@@ -230,12 +230,12 @@ describe('onBuild()', () => {
   })
 
   afterEach(() => {
-    delete process.env.URL
+    delete process.env.DEPLOY_PRIME_URL
   })
 
   test('does not set NEXTAUTH_URL if value is already set', async () => {
     const mockUserDefinedSiteUrl = chance.url()
-    process.env.URL = chance.url()
+    process.env.DEPLOY_PRIME_URL = chance.url()
 
     await moveNextDist()
 
@@ -252,13 +252,28 @@ describe('onBuild()', () => {
     expect(config.config.env.NEXTAUTH_URL).toEqual(mockUserDefinedSiteUrl)
   })
 
+  test('sets the NEXTAUTH_URL specified in the netlify.toml or in the Netlify UI', async () => {
+    const mockSiteUrl = chance.url()
+    process.env.NEXTAUTH_URL = mockSiteUrl
+
+    await moveNextDist()
+
+    await nextRuntime.onBuild(defaultArgs)
+
+    expect(onBuildHasRun(netlifyConfig)).toBe(true)
+    const config = await getRequiredServerFiles(netlifyConfig.build.publish)
+
+    expect(config.config.env.NEXTAUTH_URL).toEqual(mockSiteUrl)
+    delete process.env.NEXTAUTH_URL
+  })
+
   test('sets NEXTAUTH_URL when next-auth package is detected', async () => {
     const mockSiteUrl = chance.url()
 
     // Value represents the main address to the site and is either
     // a Netlify subdomain or custom domain set by the user.
     // See https://docs.netlify.com/configure-builds/environment-variables/#deploy-urls-and-metadata
-    process.env.URL = mockSiteUrl
+    process.env.DEPLOY_PRIME_URL = mockSiteUrl
 
     await moveNextDist()
 
@@ -272,7 +287,7 @@ describe('onBuild()', () => {
 
   test('includes the basePath on NEXTAUTH_URL when present', async () => {
     const mockSiteUrl = chance.url()
-    process.env.URL = mockSiteUrl
+    process.env.DEPLOY_PRIME_URL = mockSiteUrl
 
     await moveNextDist()