This study clarifies the importance of Erwin Piscator as the client for the “Total Theater” project (1927) by Walter Gropius and explains the following based on publications containing primary sources from Piscator and Gropius: First, the ideal vision of theater that Piscator sought is illuminated. Next, changes in form during the design process of “Total Theater” project and the relationship with Gropius’s architectural office personnel are discussed. Finally, Piscator’s influence is discussed in two respects: changes in the stage set and in the person in charge during the design of the “Total Theater.”