diff --git a/.changeset/techdocs-nice-boats-wonder.md b/.changeset/techdocs-nice-boats-wonder.md
new file mode 100644
index 0000000000..434cde841e
--- /dev/null
+++ b/.changeset/techdocs-nice-boats-wonder.md
@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-techdocs-node': patch
+---
+
+Allow usage of custom tags with sequence node type (such as the !ENV tag) in the techdocs mkdocs config.
diff --git a/plugins/techdocs-node/src/stages/generate/__fixtures__/mkdocs_with_env_tag.yml b/plugins/techdocs-node/src/stages/generate/__fixtures__/mkdocs_with_env_tag.yml
new file mode 100644
index 0000000000..cba0cd8373
--- /dev/null
+++ b/plugins/techdocs-node/src/stages/generate/__fixtures__/mkdocs_with_env_tag.yml
@@ -0,0 +1 @@
+site_name: !ENV [SITE_NAME, OTHER_NAME, 'My default site name']
diff --git a/plugins/techdocs-node/src/stages/generate/helpers.test.ts b/plugins/techdocs-node/src/stages/generate/helpers.test.ts
index 7590df94fb..f45f6034ec 100644
--- a/plugins/techdocs-node/src/stages/generate/helpers.test.ts
+++ b/plugins/techdocs-node/src/stages/generate/helpers.test.ts
@@ -78,6 +78,9 @@ const mkdocsYmlWithoutPlugins = fs.readFileSync(
 const mkdocsYmlWithAdditionalPlugins = fs.readFileSync(
   resolvePath(__filename, '../__fixtures__/mkdocs_with_additional_plugins.yml'),
 );
+const mkdocsYmlWithEnvTag = fs.readFileSync(
+  resolvePath(__filename, '../__fixtures__/mkdocs_with_env_tag.yml'),
+);
 const mockLogger = getVoidLogger();
 const warn = jest.spyOn(mockLogger, 'warn');
 
@@ -582,10 +585,16 @@ describe('helpers', () => {
       ).rejects.toThrow();
     });
 
-    it('should validate files with custom yaml tags', async () => {
+    it('should validate files with custom yaml tags (scalar)', async () => {
       await expect(
         validateMkdocsYaml(inputDir, mkdocsYmlWithExtensions.toString()),
       ).resolves.toBeUndefined();
     });
+
+    it('should validate files with custom yaml tags (sequence)', async () => {
+      await expect(
+        validateMkdocsYaml(inputDir, mkdocsYmlWithEnvTag.toString()),
+      ).resolves.toBeUndefined();
+    });
   });
 });
diff --git a/plugins/techdocs-node/src/stages/generate/helpers.ts b/plugins/techdocs-node/src/stages/generate/helpers.ts
index 349783d2bd..d70793e043 100644
--- a/plugins/techdocs-node/src/stages/generate/helpers.ts
+++ b/plugins/techdocs-node/src/stages/generate/helpers.ts
@@ -134,6 +134,14 @@ export const MKDOCS_SCHEMA = DEFAULT_SCHEMA.extend([
     instanceOf: UnknownTag,
     construct: (data: string, type?: string) => new UnknownTag(data, type),
   }),
+  new Type('', {
+    kind: 'sequence',
+    multi: true,
+    representName: o => (o as UnknownTag).type,
+    represent: o => (o as UnknownTag).data ?? '',
+    instanceOf: UnknownTag,
+    construct: (data: string, type?: string) => new UnknownTag(data, type),
+  }),
 ]);
 
 /**