['Self-efficacy can be affected by mastery experiences and somatic sensations. A novel exercise experience and associated sensations may impact self-efficacy and subsequent behaviors. We investigated the effect of a single exercise session on self-efficacy for sedentary endometrial cancer survivors compared with sedentary women of a similar age, but with no cancer history.', 'Twenty survivors and 19 controls completed an exercise session performed as a submaximal cycle ergometry test. Sensations and efficacy were measured before and after exercise. Repeated measures analysis of variance (ANOVA) was performed. Regression models were used to determine predictors of self-efficacy and subsequent exercise.', 'Self-efficacy increased for both survivors and controls, but survivors had a higher rate of increase, and the change predicted subsequent exercise. The association between exercise-related somatic sensations and self-efficacy differed between the 2 groups.'] Does an acute exercise session increase self-efficacy in sedentary endometrial cancer survivors and controls?