We seek to contribute to evidence-based teaching for management by providing an example of translating a theory into an evidence-based intervention by developing action principles; moreover, our work here shows how such an intervention affects the success of firms by way of changing managers' actions. The concept of action principle is central to this intervention, and we describe this concept with the help of action regulation theory. We conducted a randomized controlled field intervention with a theory-based 3-day program to increase personal initiative (using a pretest-posttest design and a randomized waiting control group). The sample consists of 100 small business owners in Africa (Kampala, Uganda). The intervention increased personal initiative behavior and entrepreneurial success over a 12-month period after the intervention. An increase in personal initiative behavior was responsible for the increase of entrepreneurial success (full mediation). Thus, the training led to an entrepreneurial mind-set and to an active approach toward entrepreneurial tasks.