The purpose of this study was to explore how knowledge building could support the generation of creative ideas among college students and accordingly foster their creativity. The study was conducted in Knowledge Forum (KF), a knowledge building environment, where students were encouraged to engage in idea-centered activities. Participants were 38 college students and data mainly came from students’ online activities in KF, and a pre–post test concerning creativity. The results indicate that (1) students’ divergent thinking skills were improved after taking this course; (2) students were able to generate more promising ideas and progressively build on one another’s ideas toward the end of the course; and (3) students’ performance in KF is also positively correlated with their higher-level creative skills. Overall, this study demonstrates that knowledge building activities were useful to enhance student creativity.