diff --git a/gen/python.py b/gen/python.py
index df83e6f..56a5f41 100644
--- a/gen/python.py
+++ b/gen/python.py
@@ -15,7 +15,7 @@ from midas.ast.location import Location
 ###> MidasType | Type annotations | node
 class BaseType:
     base: str
-    param: Optional[MidasType]
+    args: tuple[MidasType, ...]
 
 
 class ConstraintType:
diff --git a/midas/ast/printer.py b/midas/ast/printer.py
index c2c0704..28cf99f 100644
--- a/midas/ast/printer.py
+++ b/midas/ast/printer.py
@@ -549,7 +549,13 @@ class PythonAstPrinter(
         self._write_line("BaseType")
         with self._child_level():
             self._write_line(f"base: {node.base}")
-            self._write_optional_child("param", node.param, last=True)
+            self._write_line("args:", last=True)
+            with self._child_level():
+                for i, arg in enumerate(node.args):
+                    self._idx = i
+                    if i == len(node.args) - 1:
+                        self._mark_last()
+                    arg.accept(self)
 
     def visit_constraint_type(self, node: p.ConstraintType) -> None:
         self._write_line("ConstraintType")
diff --git a/midas/ast/python.py b/midas/ast/python.py
index 20d7279..b67a043 100644
--- a/midas/ast/python.py
+++ b/midas/ast/python.py
@@ -44,7 +44,7 @@ class MidasType(ABC):
 @dataclass(frozen=True)
 class BaseType(MidasType):
     base: str
-    param: Optional[MidasType]
+    args: tuple[MidasType, ...]
 
     def accept(self, visitor: MidasType.Visitor[T]) -> T:
         return visitor.visit_base_type(self)
diff --git a/midas/checker/python.py b/midas/checker/python.py
index 359b68b..10f82e3 100644
--- a/midas/checker/python.py
+++ b/midas/checker/python.py
@@ -761,9 +761,9 @@ class PythonTyper(
             self.reporter.warning(node.location, f"Unknown type '{node.base}'")
             return UnknownType()
 
-        if node.param is not None:
-            param: Type = self.resolve_type_expr(node.param)
-            return self.types.apply_generic(base, [param])
+        if len(node.args) != 0:
+            args: list[Type] = [self.resolve_type_expr(arg) for arg in node.args]
+            return self.types.apply_generic(base, args)
         return base
 
     def visit_constraint_type(self, node: p.ConstraintType) -> Type:
diff --git a/midas/cli/highlighter.py b/midas/cli/highlighter.py
index c131143..bced867 100644
--- a/midas/cli/highlighter.py
+++ b/midas/cli/highlighter.py
@@ -134,9 +134,9 @@ class PythonHighlighter(
 
     def visit_base_type(self, node: p.BaseType) -> None:
         self.wrap(node, "base-type")
-        if node.param is not None:
-            self.wrap(node.param, "param")
-            node.param.accept(self)
+        for arg in node.args:
+            self.wrap(arg, "arg")
+            arg.accept(self)
 
     def visit_constraint_type(self, node: p.ConstraintType) -> None:
         self.wrap(node, "constraint-type")
diff --git a/midas/cli/hl_python.css b/midas/cli/hl_python.css
index e6dc43b..899c461 100644
--- a/midas/cli/hl_python.css
+++ b/midas/cli/hl_python.css
@@ -3,7 +3,7 @@ span {
         --col: 108, 233, 108;
     }
 
-    &.param {
+    &.arg {
         --col: 103, 192, 224;
     }
 
diff --git a/midas/parser/python.py b/midas/parser/python.py
index 7839f52..9868229 100644
--- a/midas/parser/python.py
+++ b/midas/parser/python.py
@@ -300,26 +300,28 @@ class PythonParser:
             case ast.Subscript(value=ast.Name(id="Frame"), slice=schema):
                 return self._parse_frame_type(schema)
 
-            case ast.Subscript(value=ast.Name(id=name), slice=param):
+            case ast.Subscript(value=ast.Name(id=name), slice=arg):
+                args: tuple[MidasType, ...] = (
+                    tuple(self._parse_type(a) for a in arg.elts)
+                    if isinstance(arg, ast.Tuple)
+                    else (self._parse_type(arg),)
+                )
                 return BaseType(
                     location=loc,
                     base=name,
-                    param=self._parse_type(param),
+                    args=args,
                 )
 
             case ast.Name(id=name):
                 return BaseType(
                     location=loc,
                     base=name,
-                    param=None,
+                    args=(),
                 )
 
             case ast.BinOp(left=left_expr, op=ast.Add(), right=right_expr):
                 left = self._parse_type(left_expr)
                 match left:
-                    case None:
-                        raise InvalidSyntaxError()
-
                     # If chained constraints, separate base type and rebuild constraint
                     case ConstraintType(type=left_type, constraint=left_constraint):
                         constraint = ast.BinOp(
@@ -345,7 +347,7 @@ class PythonParser:
                 return BaseType(
                     location=loc,
                     base="None",
-                    param=None,
+                    args=(),
                 )
 
             case _:
diff --git a/tests/serializer/python.py b/tests/serializer/python.py
index 3904739..57e47c9 100644
--- a/tests/serializer/python.py
+++ b/tests/serializer/python.py
@@ -98,7 +98,7 @@ class PythonAstJsonSerializer(
         return {
             "_type": "BaseType",
             "base": node.base,
-            "param": self._serialize_optional(node.param),
+            "args": self._serialize_list(node.args),
         }
 
     def visit_constraint_type(self, node: ConstraintType) -> dict: