diff --git a/src/poetry/console/commands/source/add.py b/src/poetry/console/commands/source/add.py
index 541593cac1a..81b42d3fbea 100644
--- a/src/poetry/console/commands/source/add.py
+++ b/src/poetry/console/commands/source/add.py
@@ -1,11 +1,13 @@
 from __future__ import annotations
 
 from typing import TYPE_CHECKING
+from typing import Any
 from typing import ClassVar
 
 from cleo.helpers import argument
 from cleo.helpers import option
 from cleo.io.null_io import NullIO
+from tomlkit import table
 from tomlkit.items import AoT
 
 from poetry.config.source import Source
@@ -99,6 +101,13 @@ def handle(self) -> int:
             )
             return 1
 
+        # tomlkit types are awkward to work with, treat content as a mostly untyped
+        # dictionary.
+        content: dict[str, Any] = self.poetry.pyproject.data
+        if "tool" not in content:
+            content["tool"] = table()
+        if "poetry" not in content["tool"]:
+            content["tool"]["poetry"] = table()
         self.poetry.pyproject.poetry_config["source"] = sources
         self.poetry.pyproject.save()
 
diff --git a/src/poetry/poetry.py b/src/poetry/poetry.py
index 8869845d852..99baedfe2f1 100644
--- a/src/poetry/poetry.py
+++ b/src/poetry/poetry.py
@@ -88,5 +88,7 @@ def set_config(self, config: Config) -> Poetry:
     def get_sources(self) -> list[Source]:
         return [
             Source(**source)
-            for source in self.pyproject.poetry_config.get("source", [])
+            for source in self.pyproject.data.get("tool", {})
+            .get("poetry", {})
+            .get("source", [])
         ]
diff --git a/tests/console/commands/source/conftest.py b/tests/console/commands/source/conftest.py
index 264ee640e6f..9951edc2d63 100644
--- a/tests/console/commands/source/conftest.py
+++ b/tests/console/commands/source/conftest.py
@@ -63,6 +63,13 @@ def source_existing() -> Source:
     return _existing_source
 
 
+PYPROJECT_WITHOUT_POETRY_SECTION = """
+[project]
+name = "source-command-test"
+version = "0.1.0"
+"""
+
+
 PYPROJECT_WITHOUT_SOURCES = """
 [tool.poetry]
 name = "source-command-test"
@@ -99,6 +106,11 @@ def source_existing() -> Source:
 """
 
 
+@pytest.fixture
+def poetry_without_poetry_section(project_factory: ProjectFactory) -> Poetry:
+    return project_factory(pyproject_content=PYPROJECT_WITHOUT_POETRY_SECTION)
+
+
 @pytest.fixture
 def poetry_without_source(project_factory: ProjectFactory) -> Poetry:
     return project_factory(pyproject_content=PYPROJECT_WITHOUT_SOURCES)
diff --git a/tests/console/commands/source/test_add.py b/tests/console/commands/source/test_add.py
index 91a2a8cb127..f5bce3a8554 100644
--- a/tests/console/commands/source/test_add.py
+++ b/tests/console/commands/source/test_add.py
@@ -9,6 +9,8 @@
 
 
 if TYPE_CHECKING:
+    from collections.abc import Iterable
+
     from cleo.testers.command_tester import CommandTester
 
     from poetry.poetry import Poetry
@@ -25,17 +27,17 @@ def tester(
 def assert_source_added(
     tester: CommandTester,
     poetry: Poetry,
-    source_existing: Source,
-    source_added: Source,
+    added_source: Source,
+    existing_sources: Iterable[Source] = (),
 ) -> None:
     assert tester.io.fetch_error().strip() == ""
     assert (
         tester.io.fetch_output().strip()
-        == f"Adding source with name {source_added.name}."
+        == f"Adding source with name {added_source.name}."
     )
     poetry.pyproject.reload()
     sources = poetry.get_sources()
-    assert sources == [source_existing, source_added]
+    assert sources == [*existing_sources, added_source]
     assert tester.status_code == 0
 
 
@@ -46,7 +48,25 @@ def test_source_add_simple(
     poetry_with_source: Poetry,
 ) -> None:
     tester.execute(f"{source_one.name} {source_one.url}")
-    assert_source_added(tester, poetry_with_source, source_existing, source_one)
+    assert_source_added(tester, poetry_with_source, source_one, [source_existing])
+
+
+def test_source_add_simple_without_existing_sources(
+    tester: CommandTester,
+    source_one: Source,
+    poetry_without_source: Poetry,
+) -> None:
+    tester.execute(f"{source_one.name} {source_one.url}")
+    assert_source_added(tester, poetry_without_source, source_one)
+
+
+def test_source_add_simple_without_existing_poetry_section(
+    tester: CommandTester,
+    source_one: Source,
+    poetry_without_poetry_section: Poetry,
+) -> None:
+    tester.execute(f"{source_one.name} {source_one.url}")
+    assert_source_added(tester, poetry_without_poetry_section, source_one)
 
 
 def test_source_add_supplemental(
@@ -59,7 +79,7 @@ def test_source_add_supplemental(
         f"--priority=supplemental {source_supplemental.name} {source_supplemental.url}"
     )
     assert_source_added(
-        tester, poetry_with_source, source_existing, source_supplemental
+        tester, poetry_with_source, source_supplemental, [source_existing]
     )
 
 
@@ -70,7 +90,7 @@ def test_source_add_explicit(
     poetry_with_source: Poetry,
 ) -> None:
     tester.execute(f"--priority=explicit {source_explicit.name} {source_explicit.url}")
-    assert_source_added(tester, poetry_with_source, source_existing, source_explicit)
+    assert_source_added(tester, poetry_with_source, source_explicit, [source_existing])
 
 
 def test_source_add_error_no_url(tester: CommandTester) -> None:
@@ -99,7 +119,7 @@ def test_source_add_pypi(
     poetry_with_source: Poetry,
 ) -> None:
     tester.execute(name)
-    assert_source_added(tester, poetry_with_source, source_existing, source_pypi)
+    assert_source_added(tester, poetry_with_source, source_pypi, [source_existing])
 
 
 def test_source_add_pypi_explicit(
@@ -110,7 +130,7 @@ def test_source_add_pypi_explicit(
 ) -> None:
     tester.execute("--priority=explicit PyPI")
     assert_source_added(
-        tester, poetry_with_source, source_existing, source_pypi_explicit
+        tester, poetry_with_source, source_pypi_explicit, [source_existing]
     )