The theory of mind (ToM) is the ability to understand mental states in others. The previous research has highlighted age- and language-dependent effects during childhood and provided inconsistent data regarding the role of gender. Notably, these variables were rarely studied simultaneously among adolescents. Accordingly, this short longitudinal study explored age and gender differences in advanced ToM among 233 13- and 16-year-old Polish adolescents. Controlling for language, results indicated that females outperformed males in advanced ToM measurement (Ambigous Stories task). No differences were revealed between younger and older adolescents over 18 months, although for the total sample, a small increase in the quality of ToM explanations was found. Implications for gender and developmentally sensitive measurements of advanced ToM are discussed.