Cognitive changes are reported infrequently in programs targeting cardiovascular risk. We examined self-efficacy, behavioral barriers and health beliefs in a lifestyle program for drug-treated hypertensives that aimed to reduce blood pressure, antihypertensive drug needs and cardiovascular risk. In a randomized controlled trial, we compared usual care (controls) and a 4-month program focusing on weight loss, diet and exercise. Outcomes were assessed at baseline, 4 months and 1-year follow-up. Of 241 individuals randomized, 102/123 in the program and 90/118 of controls completed follow-up. In the program group, dietary barriers fell by 14% at 4 months (controls 2%, P = 0.025) and by 8% at follow-up (controls 3%, P = 0.010). Exercise barriers fell by 11% at 4 months (controls 3%, P = 0.020) and 17% (controls 4%, P = 0.002) at follow-up. Dietary self-efficacy improved by 3% at 4 months (controls -1%, P = 0.003) and by 2% at follow-up (controls -1%, P = 0.051). Exercise self-efficacy increased by 8% at 4 months (controls 3%, P < 0.001) and by 5% at follow-up (controls 3%, P = 0.130). Changes in cognitive variables predicted changes in health-related behaviors at 4 months and follow-up. A cognitively based lifestyle program in treated hypertensives is associated with improvements in cognitive measures in the shorter and longer term.