Background: Self-efficacy is a consistent correlate of physical activity, but most self-efficacy measures have not been validated in diverse populations. This study examined the construct, criterion-related, and convergent validity and internal consistency of the Self-Efficacy for Exercise Questionnaire. Methods: African American and Caucasian adults (N = 1919) from two adjacent counties in South Carolina were identified through a list-assisted random digit-dialed telephone survey. Psychometric properties of the measure were assessed by gender, race, age, education, and body weight subgroups. Results: Across all subgroups, a single-factor solution explained 93 to 98% of the common variance in an exploratory factor analysis, and all 14 items had factor loadings exceeding 0.40. Higher exercise self-efficacy was significantly associated with greater physical activity, younger age, male gender, higher education, and lower body weight, as predicted. Internal consistency was high for all subgroups (α = 0.90 to 0.94). Conclusion: The Self-Efficacy for Exercise Questionnaire appears to be a valid and reliable measure for use with diverse populations