Many believe that spatial reasoning and visualization contribute to success in engineering. To investigate this view, we a) studied how students in engineering and engineers in professional practice solved spatial reasoning problems, b) designed and implemented spatial strategy instruction, and c) characterized the impact of spatial instruction on engineering course performance. In the span of 4 years, over 500 students have used our spatial strategy instruction that includes hands-on activities, innovative computer courseware, and problem-solving assessments. We studied 153 students in an introductory engineering course. Overall, students made significant progress in spatial reasoning. In addition, gender differences in the ability to generate orthographic projections on the pre-test disappeared on the post-test. Spatial reasoning ability was a significant predictor of overall course grade, and strong spatial skills were necessary for success on the course exams. Spatial strategy instruction helps students build a repertoire of approaches for engineering problem solving and contributes to confidence in engineering, especially for women. We recommend starting instruction on spatial strategies used by practicing engineers in introductory engineering courses and building on these skills throughout the curriculum.