Computer game designers have frequently identified game complexity or “challenge” as a key variable in determining the level of enjoyment users derive from computer games. However, no technical and psychological definition of complexity exists in the gaming literature. The current paper reports on an experiment designed to test a derived relations approach to defining game complexity. Twenty three participants were recruited and exposed to a stimulus equivalence training procedure, designed to train two five-member equivalence relations. Subsequently, participants were presented with a simulated computer game in which they were required to demonstrate responding in accordance with both one-node and three-node derived stimulus equivalence relations under severe time constraints in order to gain a high score. Participants demonstrated consistently correct responding in accordance with derived relational responding. In addition, significantly more correct responses were produced at the relationally less complex (i.e., one-node) level. It is suggested that a derived relations analysis of game complexity may serve as a viable framework within which to investigate the complex processes involved in game playing.