This study aimed to investigate the relationships among mastery goal orientations (approach and avoidance), adaptive coping strategy (positive coping), and motivational beliefs (self-efficacy and task value) among middle school students in science. The study group consists of 249 students studying at four middle schools in one of the largest cities located in the eastern part of Turkey. The research data were collected using Achievement Goals Questionnaire, Academic Coping Inventory, and the Motivated Strategies for Learning Questionnaire. Structural equation modeling was performed using AMOS program to test the hypothesized relationships among constructs. The results showed that individuals with mastery goal orientation used more positive coping strategies. It was observed that individuals with higher self-efficacy had a higher ratio of using positive coping strategies. In addition, individuals with a high level of motivational beliefs used more mastery goal orientation. Furthermore, while mastery goal orientations positively predicted motivational beliefs and positive coping strategies, positive coping strategy was found to predict positively self-efficacy only. This study was a correlational study, but correlational studies did not help the establishment of a cause-effect (causality) relationship between the variables in question. Experimental studies can be conducted in the future to reveal the causes and effects related to the correlation between the relevant variables.