Even though gender-stereotypy has become a major field of scientific interest, most studies concentrated on genderdifferences or -preferences without taking into consideration developmental issues. Based on the findings on genderstereotyped attitudes at preschool-age of Kanka, Wagner, Schober and Spiel (2011), the present study analyzed the determining influences of cognitive development, children's age, and parents' gender-stereotyped attitudes on kindergarten students' implicit theories. Data was collected from both kindergarten students and their parents. While parents filled out a questionnaire, children were tested by a standardized instrument which they should experience as a fun game. The final sample included 266 children (144 girls and 122 boys aged 3;12-7;00 years) along with 148 parents' questionnaires. To meet the needs of the present study, a multicausal model was used. Corresponding to former studies, results showed more stereotyped attitudes in girls than boys. Resu lts also revealed that implicit theories of gender-stereotypy in boys and girls are based on significant influences of the child's own sex as well as cognitive development whereby crystallized intelligence seems to have the highest impact. As crystallized intelligence is based on cultural norms, it is highly related to age (significant effect) and hen ce modifiable.