diff --git a/.changes/unreleased/Under the Hood-20230906-132435.yaml b/.changes/unreleased/Under the Hood-20230906-132435.yaml
new file mode 100644
index 00000000000..27b6da20177
--- /dev/null
+++ b/.changes/unreleased/Under the Hood-20230906-132435.yaml	
@@ -0,0 +1,6 @@
+kind: Under the Hood
+body: Fix untyped functions in task/runnable.py (mypy warning)
+time: 2023-09-06T13:24:35.448782-04:00
+custom:
+  Author: michelleark
+  Issue: "8402"
diff --git a/core/dbt/task/runnable.py b/core/dbt/task/runnable.py
index 9ae987cc2dc..cce7793b598 100644
--- a/core/dbt/task/runnable.py
+++ b/core/dbt/task/runnable.py
@@ -20,6 +20,7 @@
     RunningStatus,
     RunResult,
     RunStatus,
+    BaseResult,
 )
 from dbt.contracts.state import PreviousState
 from dbt.events.contextvars import log_contextvars, task_contextvars
@@ -42,7 +43,7 @@
     FailFastError,
 )
 from dbt.flags import get_flags
-from dbt.graph import GraphQueue, NodeSelector, SelectionSpec, parse_difference
+from dbt.graph import GraphQueue, NodeSelector, SelectionSpec, parse_difference, UniqueId
 from dbt.logger import (
     DbtProcessState,
     TextOnly,
@@ -53,7 +54,7 @@
     NodeCount,
 )
 from dbt.parser.manifest import write_manifest
-from dbt.task.base import ConfiguredTask
+from dbt.task.base import ConfiguredTask, BaseRunner
 from .printer import (
     print_run_result_error,
     print_run_end_messages,
@@ -66,13 +67,13 @@
 class GraphRunnableTask(ConfiguredTask):
     MARK_DEPENDENT_ERRORS_STATUSES = [NodeStatus.Error]
 
-    def __init__(self, args, config, manifest):
+    def __init__(self, args, config, manifest) -> None:
         super().__init__(args, config, manifest)
         self._flattened_nodes: Optional[List[ResultNode]] = None
-        self._raise_next_tick = None
-        self._skipped_children = {}
+        self._raise_next_tick: Optional[DbtRuntimeError] = None
+        self._skipped_children: Dict[str, Optional[RunResult]] = {}
         self.job_queue: Optional[GraphQueue] = None
-        self.node_results = []
+        self.node_results: List[BaseResult] = []
         self.num_nodes: int = 0
         self.previous_state: Optional[PreviousState] = None
         self.previous_defer_state: Optional[PreviousState] = None
@@ -168,7 +169,7 @@ def get_runner_type(self, node):
     def result_path(self):
         return os.path.join(self.config.project_target_path, RESULT_FILE_NAME)
 
-    def get_runner(self, node):
+    def get_runner(self, node) -> BaseRunner:
         adapter = get_adapter(self.config)
         run_count: int = 0
         num_nodes: int = 0
@@ -184,7 +185,7 @@ def get_runner(self, node):
         cls = self.get_runner_type(node)
         return cls(self.config, adapter, node, run_count, num_nodes)
 
-    def call_runner(self, runner):
+    def call_runner(self, runner: BaseRunner) -> RunResult:
         uid_context = UniqueID(runner.node.unique_id)
         with RUNNING_STATE, uid_context, log_contextvars(node_info=runner.node.node_info):
             startctx = TimestampNamed("node_started_at")
@@ -292,7 +293,7 @@ def callback(result):
 
         return
 
-    def _handle_result(self, result):
+    def _handle_result(self, result: RunResult):
         """Mark the result as completed, insert the `CompileResultNode` into
         the manifest, and mark any descendants (potentially with a 'cause' if
         the result was an ephemeral model) as skipped.
@@ -388,10 +389,12 @@ def execute_nodes(self):
 
         return self.node_results
 
-    def _mark_dependent_errors(self, node_id, result, cause):
+    def _mark_dependent_errors(
+        self, node_id: str, result: RunResult, cause: Optional[RunResult]
+    ) -> None:
         if self.graph is None:
             raise DbtInternalError("graph is None in _mark_dependent_errors")
-        for dep_node_id in self.graph.get_dependent_nodes(node_id):
+        for dep_node_id in self.graph.get_dependent_nodes(UniqueId(node_id)):
             self._skipped_children[dep_node_id] = cause
 
     def populate_adapter_cache(