Working example of sinatra routes with routes inside a class: module MyMod class Application < ::Sinatra::Base get "/hello" do "potato" end get "/movies/:movie_name/actors" do { actors: [ { name: "Actor 1", character_played: "Character 1" }, { name: "Actor 2", character_played: "Character 2" } ] }.to_json end end end MyMod::Application.run!