What is the developmental course of children's gender constancy? Do other cognitive abilities such as time comprehension and false-belief understanding foster gender constancy and the subcomponents gender stability and gender consistency? We examined the development of gender constancy and its relation to time comprehension and false-belief understanding in children aged 3 to 6 years old. A new gender constancy task was designed, consisting of video sequences presenting a boy and a girl dressing up in clothes typically worn by the opposite sex and playing with toys usually played with by the opposite sex. Time comprehension was measured by a comparison of three hourglasses containing different amounts of sand (as in Bischof-Köhler, 2000). False-belief understanding was tested with an adaptation of Wimmer and Perner's (1983) seminal change-of-location task. Regression analyses revealed that false-belief understanding predicted gender constancy and gender consistency and that time comprehension predicted gender stability. These relations are discussed according to task-specific characteristics of gender constancy and a domain-general mechanism underlying these abilities.