diff --git a/readthedocs/doc_builder/backends/mkdocs.py b/readthedocs/doc_builder/backends/mkdocs.py
index 36f2e1e5d6f..0a750705ace 100644
--- a/readthedocs/doc_builder/backends/mkdocs.py
+++ b/readthedocs/doc_builder/backends/mkdocs.py
@@ -14,6 +14,8 @@
 from readthedocs.doc_builder.base import BaseBuilder
 from readthedocs.projects.constants import MKDOCS
 from readthedocs.projects.constants import MKDOCS_HTML
+from readthedocs.projects.exceptions import ProjectConfigurationError
+from readthedocs.projects.exceptions import UserFileNotFound
 
 
 log = structlog.get_logger(__name__)
@@ -44,7 +46,12 @@ def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
 
         # This is the *MkDocs* yaml file
-        self.yaml_file = self.get_yaml_config()
+        self.config_file = None
+        if self.config.mkdocs.configuration:
+            self.config_file = os.path.join(
+                self.project_path,
+                self.config.mkdocs.configuration,
+            )
 
     def get_final_doctype(self):
         """
@@ -59,7 +66,7 @@ def get_final_doctype(self):
 
         # Allow symlinks, but only the ones that resolve inside the base directory.
         with safe_open(
-            self.yaml_file,
+            self.config_file,
             "r",
             allow_symlinks=True,
             base_path=self.project_path,
@@ -68,22 +75,23 @@ def get_final_doctype(self):
             use_directory_urls = config.get("use_directory_urls", True)
             return MKDOCS if use_directory_urls else MKDOCS_HTML
 
-    def get_yaml_config(self):
-        """Find the ``mkdocs.yml`` file in the project root."""
-        mkdocs_path = self.config.mkdocs.configuration
-        if not mkdocs_path:
-            mkdocs_path = "mkdocs.yml"
-        return os.path.join(
-            self.project_path,
-            mkdocs_path,
-        )
-
     def show_conf(self):
         """Show the current ``mkdocs.yaml`` being used."""
+        if self.config_file is None:
+            raise ProjectConfigurationError(ProjectConfigurationError.MKDOCS_YAML_NOT_FOUND)
+
+        if not os.path.exists(self.config_file):
+            raise UserFileNotFound(
+                message_id=UserFileNotFound.FILE_NOT_FOUND,
+                format_values={
+                    "filename": os.path.relpath(self.config_file, self.project_path),
+                },
+            )
+
         # Write the mkdocs.yml to the build logs
         self.run(
             "cat",
-            os.path.relpath(self.yaml_file, self.project_path),
+            os.path.relpath(self.config_file, self.project_path),
             cwd=self.project_path,
         )
 
@@ -97,8 +105,9 @@ def build(self):
             "--site-dir",
             os.path.join("$READTHEDOCS_OUTPUT", "html"),
             "--config-file",
-            os.path.relpath(self.yaml_file, self.project_path),
+            os.path.relpath(self.config_file, self.project_path),
         ]
+
         if self.config.mkdocs.fail_on_warning:
             build_command.append("--strict")
         cmd_ret = self.run(
diff --git a/readthedocs/projects/exceptions.py b/readthedocs/projects/exceptions.py
index 466d09a174d..5b9d9ce7e52 100644
--- a/readthedocs/projects/exceptions.py
+++ b/readthedocs/projects/exceptions.py
@@ -9,6 +9,7 @@ class ProjectConfigurationError(BuildUserError):
 
     NOT_FOUND = "project:sphinx:conf-py-not-found"
     MULTIPLE_CONF_FILES = "project:sphinx:multiple-conf-py-files-found"
+    MKDOCS_YAML_NOT_FOUND = "project:mkdocs:yaml-not-found"
 
 
 class UserFileNotFound(BuildUserError):
diff --git a/readthedocs/projects/notifications.py b/readthedocs/projects/notifications.py
index 9b9e5d43e7a..53648da7171 100644
--- a/readthedocs/projects/notifications.py
+++ b/readthedocs/projects/notifications.py
@@ -101,7 +101,7 @@
     ),
     Message(
         id=RepositoryError.UNSUPPORTED_VCS,
-        header=_("Repository type not suported"),
+        header=_("Repository type not supported"),
         body=_(
             textwrap.dedent(
                 """
@@ -125,6 +125,19 @@
         ),
         type=ERROR,
     ),
+    Message(
+        id=ProjectConfigurationError.MKDOCS_YAML_NOT_FOUND,
+        header=_("MkDocs configuration file is missing"),
+        body=_(
+            textwrap.dedent(
+                """
+            A configuration file was not found.
+            Make sure you have a <code>mkdocs.yml</code> file in your repository.
+            """
+            ).strip(),
+        ),
+        type=ERROR,
+    ),
     Message(
         id=ProjectConfigurationError.MULTIPLE_CONF_FILES,
         header=_("Multiple Sphinx configuration files found"),