diff --git a/toolchain/check/handle_function.cpp b/toolchain/check/handle_function.cpp
index 34d655ee4ee7..0064b9edf684 100644
--- a/toolchain/check/handle_function.cpp
+++ b/toolchain/check/handle_function.cpp
@@ -194,9 +194,17 @@ static auto BuildFunctionDecl(Context& context,
   DiagnoseModifiers(context, introducer, is_definition, parent_scope_inst_id,
                     parent_scope_inst);
   bool is_extern = introducer.modifier_set.HasAnyOf(KeywordModifierSet::Extern);
-  if (introducer.modifier_set.HasAnyOf(KeywordModifierSet::Method)) {
-    context.TODO(introducer.modifier_node_id(ModifierOrder::Decl),
-                 "method modifier");
+  SemIR::FunctionFields::VirtualModifier virtual_modifier =
+      SemIR::FunctionFields::VirtualModifier::None;
+
+  if (introducer.modifier_set.HasAnyOf(KeywordModifierSet::Virtual)) {
+    virtual_modifier = SemIR::FunctionFields::VirtualModifier::Virtual;
+  }
+  if (introducer.modifier_set.HasAnyOf(KeywordModifierSet::Abstract)) {
+    virtual_modifier = SemIR::FunctionFields::VirtualModifier::Abstract;
+  }
+  if (introducer.modifier_set.HasAnyOf(KeywordModifierSet::Impl)) {
+    virtual_modifier = SemIR::FunctionFields::VirtualModifier::Impl;
   }
   if (introducer.modifier_set.HasAnyOf(KeywordModifierSet::Interface)) {
     // TODO: Once we are saving the modifiers for a function, add check that
@@ -216,7 +224,8 @@ static auto BuildFunctionDecl(Context& context,
   auto function_info =
       SemIR::Function{{name_context.MakeEntityWithParamsBase(
                           name, decl_id, is_extern, introducer.extern_library)},
-                      {.return_storage_id = return_storage_id}};
+                      {.return_storage_id = return_storage_id,
+                       .virtual_modifier = virtual_modifier}};
   if (is_definition) {
     function_info.definition_id = decl_id;
   }
diff --git a/toolchain/check/testdata/class/fail_todo_modifiers.carbon b/toolchain/check/testdata/class/todo_access_modifiers.carbon
similarity index 53%
rename from toolchain/check/testdata/class/fail_todo_modifiers.carbon
rename to toolchain/check/testdata/class/todo_access_modifiers.carbon
index 0e3f01e8839a..3a9ca04efee4 100644
--- a/toolchain/check/testdata/class/fail_todo_modifiers.carbon
+++ b/toolchain/check/testdata/class/todo_access_modifiers.carbon
@@ -4,9 +4,9 @@
 //
 // AUTOUPDATE
 // TIP: To test this file alone, run:
-// TIP:   bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/check/testdata/class/fail_todo_modifiers.carbon
+// TIP:   bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/check/testdata/class/todo_access_modifiers.carbon
 // TIP: To dump output, run:
-// TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/check/testdata/class/fail_todo_modifiers.carbon
+// TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/check/testdata/class/todo_access_modifiers.carbon
 
 // TODO: Test calls to these (member access control is not yet implemented).
 class Access {
@@ -19,42 +19,7 @@ class Access {
   protected var l: i32;
 }
 
-base class Base {
-
-  // CHECK:STDERR: fail_todo_modifiers.carbon:[[@LINE+4]]:3: ERROR: Semantics TODO: `method modifier`.
-  // CHECK:STDERR:   virtual fn H();
-  // CHECK:STDERR:   ^~~~~~~
-  // CHECK:STDERR:
-  virtual fn H();
-
-  // CHECK:STDERR: fail_todo_modifiers.carbon:[[@LINE+4]]:3: ERROR: Semantics TODO: `method modifier`.
-  // CHECK:STDERR:   impl fn I();
-  // CHECK:STDERR:   ^~~~
-  // CHECK:STDERR:
-  impl fn I();
-}
-
-abstract class Abstract {
-
-  // CHECK:STDERR: fail_todo_modifiers.carbon:[[@LINE+4]]:3: ERROR: Semantics TODO: `method modifier`.
-  // CHECK:STDERR:   abstract fn J();
-  // CHECK:STDERR:   ^~~~~~~~
-  // CHECK:STDERR:
-  abstract fn J();
-
-  // CHECK:STDERR: fail_todo_modifiers.carbon:[[@LINE+4]]:3: ERROR: Semantics TODO: `method modifier`.
-  // CHECK:STDERR:   virtual fn K();
-  // CHECK:STDERR:   ^~~~~~~
-  // CHECK:STDERR:
-  virtual fn K();
-
-  // CHECK:STDERR: fail_todo_modifiers.carbon:[[@LINE+3]]:3: ERROR: Semantics TODO: `method modifier`.
-  // CHECK:STDERR:   impl fn L();
-  // CHECK:STDERR:   ^~~~
-  impl fn L();
-}
-
-// CHECK:STDOUT: --- fail_todo_modifiers.carbon
+// CHECK:STDOUT: --- todo_access_modifiers.carbon
 // CHECK:STDOUT:
 // CHECK:STDOUT: constants {
 // CHECK:STDOUT:   %Access: type = class_type @Access [template]
@@ -67,19 +32,6 @@ abstract class Abstract {
 // CHECK:STDOUT:   %Int32: %Int32.type = struct_value () [template]
 // CHECK:STDOUT:   %.2: type = unbound_element_type %Access, i32 [template]
 // CHECK:STDOUT:   %.3: type = struct_type {.k: i32, .l: i32} [template]
-// CHECK:STDOUT:   %Base: type = class_type @Base [template]
-// CHECK:STDOUT:   %H.type: type = fn_type @H [template]
-// CHECK:STDOUT:   %H: %H.type = struct_value () [template]
-// CHECK:STDOUT:   %I.type: type = fn_type @I [template]
-// CHECK:STDOUT:   %I: %I.type = struct_value () [template]
-// CHECK:STDOUT:   %.4: type = struct_type {} [template]
-// CHECK:STDOUT:   %Abstract: type = class_type @Abstract [template]
-// CHECK:STDOUT:   %J.type: type = fn_type @J [template]
-// CHECK:STDOUT:   %J: %J.type = struct_value () [template]
-// CHECK:STDOUT:   %K.type: type = fn_type @K [template]
-// CHECK:STDOUT:   %K: %K.type = struct_value () [template]
-// CHECK:STDOUT:   %L.type: type = fn_type @L [template]
-// CHECK:STDOUT:   %L: %L.type = struct_value () [template]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: imports {
@@ -101,13 +53,9 @@ abstract class Abstract {
 // CHECK:STDOUT:   package: <namespace> = namespace [template] {
 // CHECK:STDOUT:     .Core = imports.%Core
 // CHECK:STDOUT:     .Access = %Access.decl
-// CHECK:STDOUT:     .Base = %Base.decl
-// CHECK:STDOUT:     .Abstract = %Abstract.decl
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.import = import Core
 // CHECK:STDOUT:   %Access.decl: type = class_decl @Access [template = constants.%Access] {}
-// CHECK:STDOUT:   %Base.decl: type = class_decl @Base [template = constants.%Base] {}
-// CHECK:STDOUT:   %Abstract.decl: type = class_decl @Abstract [template = constants.%Abstract] {}
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @Access {
@@ -130,41 +78,9 @@ abstract class Abstract {
 // CHECK:STDOUT:   .l [protected] = %.loc19_18
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: class @Base {
-// CHECK:STDOUT:   %H.decl: %H.type = fn_decl @H [template = constants.%H] {}
-// CHECK:STDOUT:   %I.decl: %I.type = fn_decl @I [template = constants.%I] {}
-// CHECK:STDOUT:
-// CHECK:STDOUT: !members:
-// CHECK:STDOUT:   .Self = constants.%Base
-// CHECK:STDOUT:   .H = %H.decl
-// CHECK:STDOUT:   .I = %I.decl
-// CHECK:STDOUT: }
-// CHECK:STDOUT:
-// CHECK:STDOUT: class @Abstract {
-// CHECK:STDOUT:   %J.decl: %J.type = fn_decl @J [template = constants.%J] {}
-// CHECK:STDOUT:   %K.decl: %K.type = fn_decl @K [template = constants.%K] {}
-// CHECK:STDOUT:   %L.decl: %L.type = fn_decl @L [template = constants.%L] {}
-// CHECK:STDOUT:
-// CHECK:STDOUT: !members:
-// CHECK:STDOUT:   .Self = constants.%Abstract
-// CHECK:STDOUT:   .J = %J.decl
-// CHECK:STDOUT:   .K = %K.decl
-// CHECK:STDOUT:   .L = %L.decl
-// CHECK:STDOUT: }
-// CHECK:STDOUT:
 // CHECK:STDOUT: fn @F();
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @G();
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @Int32() -> type = "int.make_type_32";
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @H();
-// CHECK:STDOUT:
-// CHECK:STDOUT: fn @I();
-// CHECK:STDOUT:
-// CHECK:STDOUT: fn @J();
-// CHECK:STDOUT:
-// CHECK:STDOUT: fn @K();
-// CHECK:STDOUT:
-// CHECK:STDOUT: fn @L();
-// CHECK:STDOUT:
diff --git a/toolchain/check/testdata/class/virtual_modifiers.carbon b/toolchain/check/testdata/class/virtual_modifiers.carbon
new file mode 100644
index 000000000000..efab3db1bb1e
--- /dev/null
+++ b/toolchain/check/testdata/class/virtual_modifiers.carbon
@@ -0,0 +1,100 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// AUTOUPDATE
+// TIP: To test this file alone, run:
+// TIP:   bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/check/testdata/class/virtual_modifiers.carbon
+// TIP: To dump output, run:
+// TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/check/testdata/class/virtual_modifiers.carbon
+
+
+base class Base {
+  virtual fn H();
+
+  impl fn I();
+}
+
+abstract class Abstract {
+  abstract fn J();
+
+  virtual fn K();
+
+  impl fn L();
+}
+
+// CHECK:STDOUT: --- virtual_modifiers.carbon
+// CHECK:STDOUT:
+// CHECK:STDOUT: constants {
+// CHECK:STDOUT:   %Base: type = class_type @Base [template]
+// CHECK:STDOUT:   %H.type: type = fn_type @H [template]
+// CHECK:STDOUT:   %.1: type = tuple_type () [template]
+// CHECK:STDOUT:   %H: %H.type = struct_value () [template]
+// CHECK:STDOUT:   %I.type: type = fn_type @I [template]
+// CHECK:STDOUT:   %I: %I.type = struct_value () [template]
+// CHECK:STDOUT:   %.2: type = struct_type {} [template]
+// CHECK:STDOUT:   %Abstract: type = class_type @Abstract [template]
+// CHECK:STDOUT:   %J.type: type = fn_type @J [template]
+// CHECK:STDOUT:   %J: %J.type = struct_value () [template]
+// CHECK:STDOUT:   %K.type: type = fn_type @K [template]
+// CHECK:STDOUT:   %K: %K.type = struct_value () [template]
+// CHECK:STDOUT:   %L.type: type = fn_type @L [template]
+// CHECK:STDOUT:   %L: %L.type = struct_value () [template]
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: imports {
+// CHECK:STDOUT:   %Core: <namespace> = namespace file.%Core.import, [template] {
+// CHECK:STDOUT:     import Core//prelude
+// CHECK:STDOUT:     import Core//prelude/operators
+// CHECK:STDOUT:     import Core//prelude/types
+// CHECK:STDOUT:     import Core//prelude/operators/arithmetic
+// CHECK:STDOUT:     import Core//prelude/operators/as
+// CHECK:STDOUT:     import Core//prelude/operators/bitwise
+// CHECK:STDOUT:     import Core//prelude/operators/comparison
+// CHECK:STDOUT:     import Core//prelude/types/bool
+// CHECK:STDOUT:   }
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: file {
+// CHECK:STDOUT:   package: <namespace> = namespace [template] {
+// CHECK:STDOUT:     .Core = imports.%Core
+// CHECK:STDOUT:     .Base = %Base.decl
+// CHECK:STDOUT:     .Abstract = %Abstract.decl
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %Core.import = import Core
+// CHECK:STDOUT:   %Base.decl: type = class_decl @Base [template = constants.%Base] {}
+// CHECK:STDOUT:   %Abstract.decl: type = class_decl @Abstract [template = constants.%Abstract] {}
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: class @Base {
+// CHECK:STDOUT:   %H.decl: %H.type = fn_decl @H [template = constants.%H] {}
+// CHECK:STDOUT:   %I.decl: %I.type = fn_decl @I [template = constants.%I] {}
+// CHECK:STDOUT:
+// CHECK:STDOUT: !members:
+// CHECK:STDOUT:   .Self = constants.%Base
+// CHECK:STDOUT:   .H = %H.decl
+// CHECK:STDOUT:   .I = %I.decl
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: class @Abstract {
+// CHECK:STDOUT:   %J.decl: %J.type = fn_decl @J [template = constants.%J] {}
+// CHECK:STDOUT:   %K.decl: %K.type = fn_decl @K [template = constants.%K] {}
+// CHECK:STDOUT:   %L.decl: %L.type = fn_decl @L [template = constants.%L] {}
+// CHECK:STDOUT:
+// CHECK:STDOUT: !members:
+// CHECK:STDOUT:   .Self = constants.%Abstract
+// CHECK:STDOUT:   .J = %J.decl
+// CHECK:STDOUT:   .K = %K.decl
+// CHECK:STDOUT:   .L = %L.decl
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: virtual fn @H();
+// CHECK:STDOUT:
+// CHECK:STDOUT: impl fn @I();
+// CHECK:STDOUT:
+// CHECK:STDOUT: abstract fn @J();
+// CHECK:STDOUT:
+// CHECK:STDOUT: virtual fn @K();
+// CHECK:STDOUT:
+// CHECK:STDOUT: impl fn @L();
+// CHECK:STDOUT:
diff --git a/toolchain/sem_ir/formatter.cpp b/toolchain/sem_ir/formatter.cpp
index 2e145dab1f43..c1a742ead08f 100644
--- a/toolchain/sem_ir/formatter.cpp
+++ b/toolchain/sem_ir/formatter.cpp
@@ -261,7 +261,25 @@ class FormatterImpl {
   // Formats a full function.
   auto FormatFunction(FunctionId id) -> void {
     const Function& fn = sem_ir_.functions().Get(id);
-    FormatEntityStart(fn.is_extern ? "extern fn" : "fn", fn.generic_id, id);
+    std::string function_start;
+    switch (fn.virtual_modifier) {
+      case FunctionFields::VirtualModifier::Virtual:
+        function_start += "virtual ";
+        break;
+      case FunctionFields::VirtualModifier::Abstract:
+        function_start += "abstract ";
+        break;
+      case FunctionFields::VirtualModifier::Impl:
+        function_start += "impl ";
+        break;
+      case FunctionFields::VirtualModifier::None:
+        break;
+    }
+    if (fn.is_extern) {
+      function_start += "extern ";
+    }
+    function_start += "fn";
+    FormatEntityStart(function_start, fn.generic_id, id);
 
     llvm::SaveAndRestore function_scope(scope_, inst_namer_->GetScopeFor(id));
 
diff --git a/toolchain/sem_ir/function.h b/toolchain/sem_ir/function.h
index 43aaed965419..4fd512a32363 100644
--- a/toolchain/sem_ir/function.h
+++ b/toolchain/sem_ir/function.h
@@ -14,6 +14,9 @@ namespace Carbon::SemIR {
 
 // Function-specific fields.
 struct FunctionFields {
+  // Kinds of virtual modifiers that can apply to functions.
+  enum class VirtualModifier { None, Virtual, Abstract, Impl };
+
   // The following members always have values, and do not change throughout the
   // lifetime of the function.
 
@@ -23,6 +26,10 @@ struct FunctionFields {
   // always present if the function has a declared return type.
   InstId return_storage_id;
 
+  // Which, if any, virtual modifier (virtual, abstract, or impl) is applied to
+  // this function.
+  VirtualModifier virtual_modifier;
+
   // The following member is set on the first call to the function, or at the
   // point where the function is defined.