diff --git a/changelog/982.bugfix.rst b/changelog/982.bugfix.rst
new file mode 100644
index 0000000000..548e13e497
--- /dev/null
+++ b/changelog/982.bugfix.rst
@@ -0,0 +1 @@
+|commands| Fix autocompletion not working for options of nested :func:`~ext.commands.injection`\s.
diff --git a/disnake/ext/commands/params.py b/disnake/ext/commands/params.py
index e72f7f5b4f..55ed5b716e 100644
--- a/disnake/ext/commands/params.py
+++ b/disnake/ext/commands/params.py
@@ -1103,13 +1103,31 @@ def collect_params(
     )
 
 
+def apply_injection_autocompleters(
+    injection: Injection, params: list[ParamInfo], location: str
+) -> None:
+    """Assign an injection's autocompleters to the matching collected params *in-place*"""
+    if not injection.autocompleters:
+        return
+
+    lookup = {p.name: p for p in params}
+    for name, func in injection.autocompleters.items():
+        param = lookup.get(name)
+        if param is None:
+            msg = f"Option '{name}' doesn't exist in '{location}'"
+            raise ValueError(msg)
+        param.autocomplete = func
+
+
 def collect_nested_params(function: Callable[..., Any]) -> list[ParamInfo]:
     """Collect all options from a function"""
     # TODO: Have these be actually sorted properly and not have injections always at the end
     _, _, paraminfos, injections = collect_params(function)
 
     for injection in injections.values():
-        paraminfos += collect_nested_params(injection.function)
+        nested = collect_nested_params(injection.function)
+        apply_injection_autocompleters(injection, nested, injection.function.__name__)
+        paraminfos += nested
 
     return sorted(paraminfos, key=lambda param: not param.required)
 
@@ -1198,14 +1216,7 @@ def expand_params(command: AnySlashCommand) -> list[Option]:
 
     for injection in injections.values():
         collected = collect_nested_params(injection.function)
-        if injection.autocompleters:
-            lookup = {p.name: p for p in collected}
-            for name, func in injection.autocompleters.items():
-                param = lookup.get(name)
-                if param is None:
-                    msg = f"Option '{name}' doesn't exist in '{command.qualified_name}'"
-                    raise ValueError(msg)
-                param.autocomplete = func
+        apply_injection_autocompleters(injection, collected, command.qualified_name)
         params += collected
 
     params = sorted(params, key=lambda param: not param.required)
diff --git a/tests/ext/commands/test_params.py b/tests/ext/commands/test_params.py
index 41c5b04787..b4c4f645a1 100644
--- a/tests/ext/commands/test_params.py
+++ b/tests/ext/commands/test_params.py
@@ -311,3 +311,56 @@ def func(
         assert cog is None
         assert inter is not None
         assert params.keys() == {"a"}
+
+
+class TestNestedInjectionAutocomplete:
+    def test_nested_injection_autocomplete(self) -> None:
+        @commands.injection()
+        def inner(a: str, b: str) -> str:
+            return a + b
+
+        @inner.autocomplete("a")
+        async def autocomp_a(inter, value) -> list[str]:
+            return [value]
+
+        @commands.injection()
+        def outer(c: str, d: str = inner) -> str:  # type: ignore[assignment]
+            return c + d
+
+        @outer.autocomplete("c")
+        async def autocomp_c(inter, value) -> list[str]:
+            return [value]
+
+        @commands.slash_command()
+        async def cmd(
+            inter: disnake.ApplicationCommandInteraction,
+            arg: str = outer,  # type: ignore[assignment]
+        ) -> None: ...
+
+        assert cmd.autocompleters.keys() == {"a", "c"}
+        assert {o.name: o.autocomplete for o in cmd.body.options} == {
+            "a": True,
+            "b": False,
+            "c": True,
+        }
+
+    def test_nested_injection_unknown_option(self) -> None:
+        @commands.injection()
+        def inner(a: str) -> str:
+            return a
+
+        @inner.autocomplete("nonexistent")
+        async def autocomp(inter, value) -> list[str]:
+            return [value]
+
+        @commands.injection()
+        def outer(b: str, c: str = inner) -> str:  # type: ignore[assignment]
+            return b + c
+
+        with pytest.raises(ValueError, match="Option 'nonexistent' doesn't exist"):
+
+            @commands.slash_command()
+            async def cmd(
+                inter: disnake.ApplicationCommandInteraction,
+                arg: str = outer,  # type: ignore[assignment]
+            ) -> None: ...