Poor spatial ability can limit success in science, technology, engineering, and mathematics (STEM) disciplines. Many initiatives aim to increase STEM achievement and degree attainment through selective recruitment of high-spatial students or targeted training to improve spatial ability. The current study examines an alternative approach to increasing achievement that includes problem-solving strategy training. In this study, we examined how training in multiple problem-solving strategies affects science achievement and its relations to sex and spatial ability. We compared 3 interventions that trained either mental imagery strategies, analytic problem-solving strategies, or their combination in the context of a college chemistry course. As predicted, students adopted more analytic strategies after analytic training, and women used significantly more analytic strategies than men after instruction. Training in the combined use of mental imagery and analytic strategies eliminated sex differences in achievement, but training in a single type of strategy resulted in a male achievement advantage. Our work demonstrates that achievement is dependent not only on spatial ability but also on strategy choice, and that strategy training offers a viable route to improving the performance of female students.