The purpose of this study is to explain the gender differences in reading achievement with the mediating role of metacognitive strategies and reading-related attitudes. Hypotheses were tested with 6890 students [3396 (49.3%) females, 3494 (50.7%) males] who participated in PISA 2018 in Turkey. The path analysis results indicated that gender had significant associations with metacognitive strategies and reading-related attitudes. One remarkable result is that gender affected metacognitive strategies about lower cognitive levels more than strategies about higher cognitive levels, and that the female advantage was reduced for upper metacognitive strategies. Additionally, reading-related attitudes, except for perception of reading competence, and metacognitive strategies were significantly associated with reading achievement. In addition, the results revealed that metacognitive strategies and reading-related attitudes, except for perception of reading competence, fully mediated gender and reading achievement. Overall, the results show that the gender difference in reading achievement is not only due to gender itself, but may also be due to differentiation of the metacognitive strategies and reading-related attitudes of girls and boys. As a result, the teaching of metacognitive strategies and development of reading-related attitudes to students are recommended, in order to reduce the gender gap in reading achievement. Limitations, practical implications, and recommendations for future research are discussed.