Purpose: The purpose of the study was to identify gender and body weight differences in Chinese adolescents' perceived expectancy value (EV) motivation in their physical education (PE) class. The study also explored the relationship between EV and adolescents' health-related fitness performances. Method: A group of seventh and eighth graders (N = 224) from China were measured on EV toward PE as well as health-related fitness levels. A two-way MANOVA test was used to examine gender and body weight differences in EV motivations. Several two-step hierarchical multiple regression analyses were conducted to examine the relationship between EV motivation and various fitness performances while controlling for the effects of gender and body weight. Results: Boys had higher expectancy beliefs and perceived their PE class as more interesting, useful, and important than girls did. Compared with overweight/obese students, students in the healthy weight group reported higher expectancy beliefs. When the effects of gender and body weight were accounted for, expectancy beliefs were the only reliable predictor influencing adolescents' cardiorespiratory as well as muscular strength/endurance fitness levels. Discussion/Conclusion: Physical educators should use various teaching strategies to enhance students' expectancy beliefs and task values. This is especially important for female students and overweight/obese students.