Gender differences in mathematical ability is a topic that has been extensively studied in the area of mathematics. The reason that many studies have been conducted about the topic for years is the contradictory results of different studies. The aim of this study was to investigate gender differences in general mathematical ability and sub-tests of mathematical ability. With this purpose, the Test of Mathematical Talent (TMT) developed to identify talented students in mathematics was used as data collection tool. TMT includes eleven sub-tests as number series, numerical analogy, linear logic, conditional logic, algebra, numbers-measurement, geometry, statistics and probability, figurative rotation, figurative series and figurative analogy. The study included 1393 6th grade students who applied for admission to the Education Programs for Talented Students (ÜYEP), an after school program for mathematically and scientifically talented students. 683 of the participants were girls and 710 of the participants were boys. The gender differences in mathematical ability were investigated by general mathematical ability, sub-tests and top %10 of the participants. Two-factor ANOVA, one-factor MANOVA and Mann-Whitney U Test were used to investigate gender differences in general mathematical ability, its sub-tests and top %10, respectively. Findings show that there was a significant gender difference in terms of general mathematical ability favoring boys. Boys also scored significantly higher than girls in number series, numerical analogy, linear logic, conditional logic, algebra, numbers-measurement and figurative rotation sub-tests while girls’ and boys’ performance did not differ in geometry, statistics and probability, figurative series and figurative analogy sub-tests. Although the proportion of boys in the top %10 was significantly higher than that of girls, their performance level did not significantly differ in mathematical ability and its sub-tests.