Students' attitudes towards science is a long-standing topic in science education. Among various sub-constructs of attitudes towards science, students' motives for learning science and their self-efficacy in science learning may be the most frequently studied. Drawing from the expectancy-value theory (EVT), this study explored the extent to which the interaction between motives for learning science and self-efficacy in science learning can predict students' behavioral tendency to learn science in the classroom. The subjects were 345 tenth graders in Hong Kong. The results of stepwise multiple regression analyses indicated that while there was a significant interaction effect between utilitarian motive for leaning science and self-efficacy in learning science in their impacts on students' science learning, such effect was not found for intrinsic motive. Significant gender differences were revealed favoring boys in all four aspects covered in this study. The moderation of the levels of school on gender difference was found significant in students' intrinsic motive and behavioral tendency to learn science in classroom. This study enriches both the theories about attitudes towards science and the EVT through revealing the value-specific feature of the expectancy × value interaction. It is necessary to consider the multiplicative effect emphasized in the EVT when teachers consider the strategies to influence students' motives and self-efficacy so as to enhance students' engagement into science learning.