Integrating the dynamic self-regulatory framework with the motivational self-regulation perspective, we theorize and test how and when creative self-efficacy increases individual creativity at the within-person level. Conceptualizing creative process engagement as a self-regulation effort, we theorize that creative process engagement mediates the within-person effect of creative self-efficacy on individual creativity. We further explore how creative self-efficacy and chronic regulatory focus interact to affect the within-person mediating effect. A sample of 145 R&D workers provided two monthly reports for their creative activities and experiences over 8 months. The findings provide empirical support for the hypothesized mediating mechanism. At the within-person level, creative process engagement mediates the relationship between creative self-efficacy and individual creativity. The results also show that chronic regulatory focus moderated the mediated relationship. Specifically, creative self-efficacy is positively related to individual creativity for employees with a strong prevention focus and negatively related to individual creativity for employees with a strong promotion focus.