The main purpose of the present study is to investigate middle school students' science self-efficacy as well as its sources and outcomes as a function of gender. Bandura's hypothesized sources of self-efficacy (i.e., mastery experience, vicarious experience, verbal persuasion, and emotional arousal) in addition to being inviting with self and inviting with others were examined as sources of self-efficacy, while cognitive and metacognitive strategy use was examined as an outcome of self-efficacy. A total of 1,932 students participated in the study and were administered self-report instruments. Results showed that the relationship between science self-efficacy and its proposed sources does not change as a function of gender. All proposed sources, except for vicarious experience, were found to be significantly related to students' scientific self-efficacy. Moreover, girls were found to experience significantly more emotional arousal and to send positive messages to others more than boys. On the other hand, no gender difference was found concerning science self-efficacy and strategy use. The findings also revealed a positive association between science self-efficacy and strategy use. Overall, findings supported Bandura's conception of self-efficacy and suggested invitations as additional sources of self-efficacy.