In this study we examined the relationship between teacher and student intrinsic motivation in project-based learning. The participants were 126 Hong Kong secondary school teachers and their 631 students who completed evaluation questionnaires after a semester-long project-based learning program. Both teachers and students were asked to indicate their motivation in the program, and students were also asked to report the instructional support they received from their teachers. The results of hierarchical linear modeling analyses showed that teacher intrinsic motivation predicted student intrinsic motivation directly as well as indirectly through the mediation of instructional support. When teachers reported higher intrinsic motivation in the program, their students tended to perceive receiving more support from them and to report higher intrinsic motivation in the learning experience.