This study investigates the relation between Viola Spolin's methodology of theatrical education and Konstantin Stanislavski's. It elucidates major similarities and differences between Spolin's theater games and Stanislavski's system in more detail than previous research. This investigation belongs to a research project on the origins of Spolin's games, which have been widely adopted in contemporary education. The present study reveals that Spolin shared several essential ideas with Stanislavski: the application of improvisation to theatrical training, the objection to director-centered production, the emphasis on intuition and spontaneity in the creative process, the evocative function of the theatrical situation/circumstances, the value of emotion and memory for creation, and the concept of energy exchange in theatrical communication. In addition, she introduced several games highly similar to the exercises in Stanislavski's system, for example, Exposure, Space Objects, Gibberish, and No Motion Warm-Up. Spolin presumably adopted, directly or indirectly, at least some of the key concepts and exercises from Stanislavski's theatrical works. However, she refused some aspects of Stanislavski's system: the teacher's privilege of approval/disapproval, the strong emphasis on imagination, the psychological view of emotion and memory, and the inhibition of direct communication between actors and the audience. Instead, Spolin developed several unique ideas for theatrical education, for instance, teachers as fellow players, contact as a way to get out into the theatrical environment, body memory as opposed to mental retention, and audience members as fellow players. The results of this study thus provide the insight that Stanislavski's system had a more profound influence, whether as a positive or negative model, on Spolin's theory and practice than as illustrated by previous studies. In this way, the present study casts light upon a significant phase of the history of theatrical methods in education and contributes to a better understanding of the characteristics and underlying philosophy of theater games.