The aim of this study was to examine the effects of a self-efficacy program for persons with type 2 diabetes in Taiwan. A randomized controlled trial was designed (n = 145), with 72 participants in the intervention group and 73 in the control group. The participants were pretested to establish a baseline and then posttests were undertaken 3 and 6 months after the baseline data were collected. The participants in the intervention group received the standard diabetes education program and an additional self-efficacy program. The scores for efficacy expectations, outcome expectations, and self-care activities had significantly increased in the intervention group at the 3 and 6 month follow-ups, when compared to those of the control group. A smaller proportion of the participants in the intervention group had been hospitalized or had visited an emergency room than in the control group at the 6 month follow-up. This study revealed that a self-efficacy program for diabetes was acceptable and effective in the short term in the self-management of persons with type 2 diabetes.