What does the word “serious” (spoudaios) mean and how exactly is it opposed to play (paidia)? If play is for immediate pleasure, and the serious defers that pleasure for the sake of longer-term goals, how is it possible for there to be something like “serious play”, a phenomenon so often remarked upon by play theorists and regularly attested in Greek? It is argued that serious play is "goal-oriented" play, but with significant qualifications regarding what a “goal” might mean for activities in which pleasure is available at each and every moment. Passages studied include Parysatis’ dice-game in Plutarch’s Life of Artaxerxes and Cyrus’ king-game in the first book of Herodotus’ Histories. These players are “serious” inasmuch as they are focused on the goals and rules of their game. As such, at the end, it is suggested that more- and less-serious play might be articulated in terms of tragedy and comedy: in tragic play, rules and goals persist, while in comic play they are erased and recreated with each passing fancy.