diff --git a/sphinx_needs/data.py b/sphinx_needs/data.py
index a36e362e3..af9f2b3dd 100644
--- a/sphinx_needs/data.py
+++ b/sphinx_needs/data.py
@@ -200,6 +200,11 @@ class NeedsInfoType(NeedsBaseDataType):
     query: str
     url: str
 
+    only_expressions: list[str]
+    """List of parent only expressions, from outer to inner.
+    Note this key is only present if there are any only expressions.
+    """
+
     # Note there are also:
     # - dynamic default options that can be set by needs_extra_options config
     # - dynamic global options that can be set by needs_global_options config
diff --git a/sphinx_needs/directives/need.py b/sphinx_needs/directives/need.py
index 7863b161f..dae4cb1d7 100644
--- a/sphinx_needs/directives/need.py
+++ b/sphinx_needs/directives/need.py
@@ -7,6 +7,7 @@
 from docutils import nodes
 from docutils.parsers.rst.states import RSTState, RSTStateMachine
 from docutils.statemachine import StringList
+from sphinx import addnodes
 from sphinx.addnodes import desc_name, desc_signature
 from sphinx.application import Sphinx
 from sphinx.environment import BuildEnvironment
@@ -309,7 +310,8 @@ def purge_needs(app: Sphinx, env: BuildEnvironment, docname: str) -> None:
 
 def analyse_need_locations(app: Sphinx, doctree: nodes.document) -> None:
     """Determine the location of each need in the doctree,
-    relative to its parent section(s) and need(s).
+    relative to its parent section(s) and need(s),
+    and also note any parent ``only`` expressions.
 
     This data is added to the need's data stored in the Sphinx environment,
     so that it can be used in tables and filters.
@@ -361,6 +363,16 @@ def analyse_need_locations(app: Sphinx, doctree: nodes.document) -> None:
             need_info["parent_needs"] = parent_needs
             need_info["parent_need"] = parent_needs[0]
 
+        # find any parent only expressions, and note them on the need data item
+        expressions = []
+        parent: nodes.Element = need_node
+        while parent := getattr(parent, "parent", None):  # type: ignore
+            if isinstance(parent, addnodes.only):  # noqa: SIM102
+                if expr := parent.get("expr"):
+                    expressions.append(expr)
+        if expressions:
+            need_info["only_expressions"] = expressions[::-1]
+
         if need_node.get("hidden"):
             hidden_needs.append(need_node)
 
diff --git a/tests/doc_test/doc_build_only/conf.py b/tests/doc_test/doc_build_only/conf.py
new file mode 100644
index 000000000..dbe2ad57f
--- /dev/null
+++ b/tests/doc_test/doc_build_only/conf.py
@@ -0,0 +1,4 @@
+version = "1"
+extensions = ["sphinx_needs"]
+
+needs_build_json = True
diff --git a/tests/doc_test/doc_build_only/index.rst b/tests/doc_test/doc_build_only/index.rst
new file mode 100644
index 000000000..e66a47df0
--- /dev/null
+++ b/tests/doc_test/doc_build_only/index.rst
@@ -0,0 +1,20 @@
+Title
+=====
+
+.. req:: Requirement 1
+   :id: REQ_1
+
+.. only:: html
+
+   .. req:: Requirement 2
+      :id: REQ_2
+
+   .. req:: Requirement 3
+      :id: REQ_3
+
+.. only:: not something
+
+   .. only:: other
+
+      .. req:: Requirement 4
+         :id: REQ_4
diff --git a/tests/test_doc_build_only.py b/tests/test_doc_build_only.py
new file mode 100644
index 000000000..7973ad5e5
--- /dev/null
+++ b/tests/test_doc_build_only.py
@@ -0,0 +1,27 @@
+import json
+from pathlib import Path
+
+import pytest
+
+
+@pytest.mark.parametrize(
+    "test_app",
+    [{"buildername": "html", "srcdir": "doc_test/doc_build_only", "no_plantuml": True}],
+    indirect=True,
+)
+def test_doc_build_only(test_app):
+    app = test_app
+
+    app.build()
+    assert app._warning.getvalue() == ""
+
+    needs = json.loads(Path(app.outdir, "needs.json").read_text("utf8"))
+    id_to_expr = {
+        k: v.get("only_expressions") for k, v in needs["versions"]["1"]["needs"].items()
+    }
+    assert id_to_expr == {
+        "REQ_1": None,
+        "REQ_2": ["html"],
+        "REQ_3": ["html"],
+        "REQ_4": ["not something", "other"],
+    }