Each fictional world that adults create has its own distinct properties, separating it from other fictional worlds. Here we explore whether this separation also exists for young children's pretend game worlds. Studies 1 and 1A set up two simultaneous games and encouraged children to create appropriate pretend identities for coloured blocks. When prompted with a situation that required the use of a Game 1 object in Game 2, 3- and 4-year-olds were reluctant to move pretend objects between games, even when the alternative-world object was explicitly highlighted as a possible choice. Study 2 found the same effect when the two game worlds were presented sequentially. This suggests that, even for young children, multiple pretend game worlds are kept psychologically separate.