The objective was to examine the relationship between self-efficacy and subsequent weight loss during a 6-month weight loss intervention in 90 white early postmenopausal healthy women. We hypothesized that participants with higher self-efficacy scores, either at baseline or follow-up, would lose more weight than those with lower scores. Each participant received a balanced meal plan with reduced energy intake. Nutritional and behavioral sessions were provided every 2 weeks during the first 3 months. Weight and height were measured at baseline, every 2 weeks in the first 3 months, and at month 6. Three-day dietary and physical activity records and Weight Efficacy Lifestyle Questionnaire were completed at the same intervals. At month 6, participants lost 3.6 ± 4.1 kg or 4.4% (mean ± SD) and decreased in weight from 82.2 ± 11.1 kg to 77.6 ± 11.4 kg (P < .001). When participants were divided into groups based on weight loss success (<5% or ≥5% of initial weight), logistic regression (controlling for age, energy intake, physical activity, attendance at group sessions, and previous weight loss attempts) demonstrated that higher self-efficacy for the Availability of Food subscale of Weight Efficacy Lifestyle Questionnaire (95% confidence interval, 1.03-1.17) and total self-efficacy (95% confidence interval, 1.00-1.04) were associated with a greater likelihood of losing 5% or more of initial weight. Overall, participants who had higher total self-efficacy and self-efficacy to resist eating when food was available were able to lose more weight. Therefore, cognitive-behavioral efforts promoting self-efficacy may be useful for bolstering individual's confidence to resist eating under various conditions and thereby improve weight loss outcomes. © 2011 Elsevier Inc.