In organizations and educational institutions, creativity trainings are the preferred approach to enhancing individual creative abilities. However, three issues regarding these trainings still remain largely unsolved. First, the question of how long-lasting creativity training effects are has not been sufficiently answered so far. Second, the question arises whether all participants benefit from such trainings equally in terms of their creative performance (CP). Third, an increasing number of studies have shown that creativity trainings may also be able to increase participants' creative self-efficacy (CSE), that is, the confidence in one's own creativity. Other studies, however, did not find evidence for this effect. Therefore, this article aims to address these issues by analyzing data from three measurement waves. Results reveal that participants' CP increased during the training and decreased only slightly 4 weeks after the training. Additionally, we found an effect of diminishing training returns in that the higher a participant's CP before the training the lower the training effect was. In contrast to most prior literature, we found no support for an effect of creativity training on participants' CSE. We discuss these findings and offer implications for both theory and practice. Finally, we state this study's limitations and derive avenues for further research.