diff --git a/spec/ameba/rules/type_names_spec.cr b/spec/ameba/rules/type_names_spec.cr
new file mode 100644
index 00000000..04da8ad9
--- /dev/null
+++ b/spec/ameba/rules/type_names_spec.cr
@@ -0,0 +1,60 @@
+require "../../spec_helper"
+
+module Ameba
+  subject = Rules::TypeNames.new
+
+  private def it_reports_name(content, expected)
+    it "reports type name #{expected}" do
+      s = Source.new content
+      Rules::TypeNames.new.catch(s).should_not be_valid
+      s.errors.first.message.should contain expected
+    end
+  end
+
+  describe Rules::TypeNames do
+    it "passes if type names are camelcased" do
+      s = Source.new %(
+        class ParseError < Exception
+        end
+
+        module HTTP
+          class RequestHandler
+          end
+        end
+
+        alias NumericValue = Float32 | Float64 | Int32 | Int64
+
+        lib LibYAML
+        end
+
+        struct TagDirective
+        end
+
+        enum Time::DayOfWeek
+        end
+      )
+      subject.catch(s).should be_valid
+    end
+
+    it_reports_name "class My_class; end", "MyClass"
+    it_reports_name "module HTT_p; end", "HTTP"
+    it_reports_name "alias Numeric_value = Int32", "NumericValue"
+    it_reports_name "lib Lib_YAML; end", "LibYAML"
+    it_reports_name "struct Tag_directive; end", "TagDirective"
+    it_reports_name "enum Time_enum::Day_of_week; end", "TimeEnum::DayOfWeek"
+
+    it "reports rule, pos and message" do
+      s = Source.new %(
+        class My_class
+        end
+      )
+      subject.catch(s).should_not be_valid
+      error = s.errors.first
+      error.rule.should_not be_nil
+      error.pos.should eq 2
+      error.message.should eq(
+        "Type name should be camelcased: MyClass, but it was My_class"
+      )
+    end
+  end
+end
diff --git a/src/ameba/ast/traverse.cr b/src/ameba/ast/traverse.cr
index be71e3ab..f711f3db 100644
--- a/src/ameba/ast/traverse.cr
+++ b/src/ameba/ast/traverse.cr
@@ -2,29 +2,36 @@ require "compiler/crystal/syntax/*"
 
 module Ameba::AST
   NODE_VISITORS = [
+    Alias,
     Call,
     Case,
+    ClassDef,
     Def,
+    EnumDef,
     If,
+    LibDef,
+    ModuleDef,
     StringInterpolation,
     Unless,
   ]
 
+  abstract class Visitor < Crystal::Visitor
+    @rule : Rule
+    @source : Source
+
+    def initialize(@rule, @source)
+      parser = Crystal::Parser.new(@source.content)
+      parser.filename = @source.path
+      parser.parse.accept self
+    end
+
+    def visit(node : Crystal::ASTNode)
+      true
+    end
+  end
+
   {% for name in NODE_VISITORS %}
-    class {{name}}Visitor < Crystal::Visitor
-      @rule : Rule
-      @source : Source
-
-      def initialize(@rule, @source)
-        parser = Crystal::Parser.new(@source.content)
-        parser.filename = @source.path
-        parser.parse.accept self
-      end
-
-      def visit(node : Crystal::ASTNode)
-        true
-      end
-
+    class {{name}}Visitor < Visitor
       def visit(node : Crystal::{{name}})
         @rule.test @source, node
       end
diff --git a/src/ameba/rules/type_names.cr b/src/ameba/rules/type_names.cr
new file mode 100644
index 00000000..e29df1dd
--- /dev/null
+++ b/src/ameba/rules/type_names.cr
@@ -0,0 +1,88 @@
+module Ameba::Rules
+  # A rule that enforces type names in camelcase manner.
+  #
+  # For example, these are considered valid:
+  #
+  # ```
+  # class ParseError < Exception
+  # end
+  #
+  # module HTTP
+  #   class RequestHandler
+  #   end
+  # end
+  #
+  # alias NumericValue = Float32 | Float64 | Int32 | Int64
+  #
+  # lib LibYAML
+  # end
+  #
+  # struct TagDirective
+  # end
+  #
+  # enum Time::DayOfWeek
+  # end
+  # ```
+  #
+  # And these are invalid type names
+  #
+  # ```
+  # class My_class
+  # end
+  #
+  # module HTT_p
+  # end
+  #
+  # alias Numeric_value = Int32
+  #
+  # lib Lib_YAML
+  # end
+  #
+  # struct Tag_directive
+  # end
+  #
+  # enum Time_enum::Day_of_week
+  # end
+  # ```
+  #
+  struct TypeNames < Rule
+    def test(source)
+      [
+        AST::ClassDefVisitor,
+        AST::EnumDefVisitor,
+        AST::ModuleDefVisitor,
+        AST::AliasVisitor,
+        AST::LibDefVisitor,
+      ].each(&.new self, source)
+    end
+
+    private def check_node(source, node)
+      name = node.name.to_s
+      expected = name.camelcase
+      return if expected == name
+
+      source.error self, node.location.try &.line_number,
+        "Type name should be camelcased: #{expected}, but it was #{name}"
+    end
+
+    def test(source, node : Crystal::ClassDef)
+      check_node(source, node)
+    end
+
+    def test(source, node : Crystal::Alias)
+      check_node(source, node)
+    end
+
+    def test(source, node : Crystal::LibDef)
+      check_node(source, node)
+    end
+
+    def test(source, node : Crystal::EnumDef)
+      check_node(source, node)
+    end
+
+    def test(source, node : Crystal::ModuleDef)
+      check_node(source, node)
+    end
+  end
+end