diff --git a/multinet/uploaders/csv.py b/multinet/uploaders/csv.py
index 3dc50895..15d41e9c 100644
--- a/multinet/uploaders/csv.py
+++ b/multinet/uploaders/csv.py
@@ -57,16 +57,46 @@ def flask_response(self) -> FlaskTuple:
         return ("Could not read CSV data", "415 Unsupported Media Type")
 
 
-def validate_csv(
-    rows: Sequence[MutableMapping], key_field: str = "_key", overwrite: bool = False
-) -> None:
-    """Perform any necessary CSV validation, and return appropriate errors."""
+def is_edge_table(rows: Sequence[MutableMapping]) -> bool:
+    """Determine if this table should be treated as an edge table."""
+    fieldnames = rows[0].keys()
+    return "_from" in fieldnames and "_to" in fieldnames
+
+
+def is_node_table(rows: Sequence[MutableMapping], key_field: str) -> bool:
+    """Determine if this table should be treated as a node table."""
+    fieldnames = rows[0].keys()
+    return key_field != "_key" or "_key" in fieldnames
+
+
+def validate_edge_table(rows: Sequence[MutableMapping]) -> None:
+    """Validate that the given table is a valid edge table."""
     data_errors: List[ValidationFailure] = []
 
-    if not rows:
-        raise ValidationFailed([MissingBody()])
+    # Checks that a cell has the form table_name/key
+    valid_cell = re.compile("[^/]+/[^/]+")
+
+    for i, row in enumerate(rows):
+        fields: List[str] = []
+        if not valid_cell.match(row["_from"]):
+            fields.append("_from")
+        if not valid_cell.match(row["_to"]):
+            fields.append("_to")
+
+        if fields:
+            # i+2 -> +1 for index offset, +1 due to header row
+            data_errors.append(InvalidRow(fields=fields, row=i + 2))
+
+    if len(data_errors) > 0:
+        raise ValidationFailed(data_errors)
+
 
+def validate_node_table(
+    rows: Sequence[MutableMapping], key_field: str, overwrite: bool
+) -> None:
+    """Validate that the given table is a valid node table."""
     fieldnames = rows[0].keys()
+    data_errors: List[ValidationFailure] = []
 
     if key_field != "_key" and key_field not in fieldnames:
         data_errors.append(KeyFieldDoesNotExist(key=key_field))
@@ -76,39 +106,33 @@ def validate_csv(
         data_errors.append(KeyFieldAlreadyExists(key=key_field))
         raise ValidationFailed(data_errors)
 
-    if key_field in fieldnames:
-        # Node Table, check for key uniqueness
-        keys = [row[key_field] for row in rows]
-        unique_keys: Set[str] = set()
-        for key in keys:
-            if key in unique_keys:
-                data_errors.append(DuplicateKey(key=key))
-            else:
-                unique_keys.add(key)
-
-    elif "_from" in fieldnames and "_to" in fieldnames:
-        # Edge Table, check that each cell has the correct format
-        valid_cell = re.compile("[^/]+/[^/]+")
-
-        for i, row in enumerate(rows):
-            fields: List[str] = []
-            if not valid_cell.match(row["_from"]):
-                fields.append("_from")
-            if not valid_cell.match(row["_to"]):
-                fields.append("_to")
-
-            if fields:
-                # i+2 -> +1 for index offset, +1 due to header row
-                data_errors.append(InvalidRow(fields=fields, row=i + 2))
-
-    else:
-        # Unsupported Table, error since we don't know what's coming in
-        data_errors.append(UnsupportedTable())
+    keys = (row[key_field] for row in rows)
+    unique_keys: Set[str] = set()
+    for key in keys:
+        if key in unique_keys:
+            data_errors.append(DuplicateKey(key=key))
+        else:
+            unique_keys.add(key)
 
     if len(data_errors) > 0:
         raise ValidationFailed(data_errors)
 
 
+def validate_csv(
+    rows: Sequence[MutableMapping], key_field: str, overwrite: bool
+) -> None:
+    """Perform any necessary CSV validation, and return appropriate errors."""
+    if not rows:
+        raise ValidationFailed([MissingBody()])
+
+    if is_node_table(rows, key_field):
+        validate_node_table(rows, key_field, overwrite)
+    elif is_edge_table(rows):
+        validate_edge_table(rows)
+    else:
+        raise ValidationFailed([UnsupportedTable()])
+
+
 def set_table_key(rows: List[Dict[str, str]], key: str) -> List[Dict[str, str]]:
     """Update the _key field in each row."""
     new_rows: List[Dict[str, str]] = []
diff --git a/test/test_csv_uploader.py b/test/test_csv_uploader.py
index 5be5a3c2..758cc24e 100644
--- a/test/test_csv_uploader.py
+++ b/test/test_csv_uploader.py
@@ -30,7 +30,7 @@ def test_missing_key_field():
 
     correct = UnsupportedTable().asdict()
     with pytest.raises(ValidationFailed) as v_error:
-        validate_csv(rows)
+        validate_csv(rows, key_field="_key", overwrite=False)
 
     validation_resp = v_error.value.errors
     assert len(validation_resp) == 1
@@ -44,7 +44,7 @@ def test_invalid_key_field():
 
     correct = KeyFieldDoesNotExist(key=invalid_key).asdict()
     with pytest.raises(ValidationFailed) as v_error:
-        validate_csv(rows, key_field=invalid_key)
+        validate_csv(rows, key_field=invalid_key, overwrite=False)
 
     validation_resp = v_error.value.errors
     assert len(validation_resp) == 1
@@ -83,7 +83,7 @@ def test_duplicate_keys():
     """Test that duplicate keys are handled properly."""
     rows = read_csv("clubs_invalid_duplicate_keys.csv")
     with pytest.raises(ValidationFailed) as v_error:
-        validate_csv(rows)
+        validate_csv(rows, key_field="_key", overwrite=False)
 
     validation_resp = v_error.value.errors
     correct = [err.asdict() for err in [DuplicateKey(key="2"), DuplicateKey(key="5")]]
@@ -94,7 +94,7 @@ def test_invalid_headers():
     """Test that invalid headers are handled properly."""
     rows = read_csv("membership_invalid_syntax.csv")
     with pytest.raises(ValidationFailed) as v_error:
-        validate_csv(rows)
+        validate_csv(rows, key_field="_key", overwrite=False)
 
     validation_resp = v_error.value.errors
     correct = [