Self-efficacy as an outcome evaluation variable for school personnel prevention training was investigated. A 3-week training institute, Enhancing Student Well-Being, is based on a holistic student well-being construct, with special emphasis given to the prevention of illegal substance use among youth. A measure of self-efficacy, including components of efficacy and outcome expectations, showed significant differences between trained educators and a comparison group of educators. At follow-up, the trained educators retained much of the self-efficacy gains realized during training. Self-efficacy was a viable variable for evaluating prevention training of school personnel.