diff --git a/haystack/components/converters/file_to_file_content.py b/haystack/components/converters/file_to_file_content.py
index 1e3b9c7d1fb..2a66a606bbf 100644
--- a/haystack/components/converters/file_to_file_content.py
+++ b/haystack/components/converters/file_to_file_content.py
@@ -82,8 +82,12 @@ def run(
                 continue
 
             base64_data = base64.b64encode(bytestream.data).decode("utf-8")
+            # ``normalize_metadata`` returns the same dict object for every source when ``extra`` is a
+            # single dict (or ``None``), so give each FileContent its own copy. Otherwise mutating one
+            # file's ``extra`` downstream would leak into all the others. The other converters avoid this
+            # implicitly by merging ``extra`` into a fresh ``{**bytestream.meta, ...}`` dict.
             file_content = FileContent(
-                base64_data=base64_data, mime_type=bytestream.mime_type, filename=filename, extra=extra_dict
+                base64_data=base64_data, mime_type=bytestream.mime_type, filename=filename, extra=dict(extra_dict)
             )
             file_contents.append(file_content)
 
diff --git a/releasenotes/notes/fix-file-to-file-content-shared-extra-4d0f1d099ab3d226.yaml b/releasenotes/notes/fix-file-to-file-content-shared-extra-4d0f1d099ab3d226.yaml
new file mode 100644
index 00000000000..244fbd964e9
--- /dev/null
+++ b/releasenotes/notes/fix-file-to-file-content-shared-extra-4d0f1d099ab3d226.yaml
@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fixed ``FileToFileContent`` sharing a single ``extra`` dictionary across all produced ``FileContent``
+    objects when ``extra`` is passed as one dict (or left as ``None``). Each ``FileContent`` now gets its
+    own copy, so mutating one file's ``extra`` no longer leaks into the others.
diff --git a/test/components/converters/test_file_to_file_content.py b/test/components/converters/test_file_to_file_content.py
index 7476b02df3f..c3370b29f28 100644
--- a/test/components/converters/test_file_to_file_content.py
+++ b/test/components/converters/test_file_to_file_content.py
@@ -113,6 +113,20 @@ def test_run_with_extra_list(self) -> None:
         assert results["file_contents"][0].extra == {"key": "value1"}
         assert results["file_contents"][1].extra == {"key": "value2"}
 
+    def test_run_with_extra_dict_does_not_share_reference(self) -> None:
+        # A single ``extra`` dict is applied to every source; each FileContent must get its own copy
+        # so that mutating one file's ``extra`` downstream does not leak into the others.
+        converter = FileToFileContent()
+        sources = ["./test/test_files/txt/doc_1.txt", "./test/test_files/txt/doc_2.txt"]
+        results = converter.run(sources=sources, extra={"tenant": "acme"})
+
+        file_contents = results["file_contents"]
+        assert len(file_contents) == 2
+        assert file_contents[0].extra is not file_contents[1].extra
+
+        file_contents[0].extra["page"] = 1
+        assert "page" not in file_contents[1].extra
+
     def test_run_skips_empty_files_among_valid(self, caplog) -> None:
         byte_stream_empty = ByteStream(data=b"")
         valid_source = "./test/test_files/txt/doc_1.txt"