The purpose of the current study was to explore the nature of the underlying relationship between creativity fostering teacher behavior and student creative achievement in science activities. In doing so, we examined the mediating effect of intrinsic motivation on the relationship between creativity fostering teacher behavior and student creative achievement in science activities, and the moderating effect of openness to experience. We conducted a two-wave survey study in three high schools in China and obtained data from 1035 students. Results from ordinary least squares regression analysis showed that creativity fostering teacher behavior was positively related to student creative achievement in science activities. We found that students' intrinsic motivation mediated the relationship between creativity fostering teacher behavior and student creative achievement. When a student had a high level of openness to experience, the relationship between intrinsic motivation and creative achievement was stronger. In addition, we discussed the implications and limitations of our study, as well as suggestions for future research.