This study examined whether controlling for social desirability improved the association between self-reported and objectively measured physical activity among adolescent males and the extent that psychosocial variables predict physical activity after controlling for social desirability. Participants (n=447) were 10- to 14-year old Houston Boy Scouts. Participants completed self-reports of physical activity, sedentary behavior, preferences, self-efficacy and social desirability and wore an MTI accelerometer for 3 days. Correlations were conducted among variables. Regression models were performed to examine the relationships between objectively measured (accelerometer) and self-reported physical activity, objectively measured physical activity and psychosocial variables and self-reports of physical activity and psychosocial variables. All models controlled for social desirability. There were weak associations between self-reported and objectively measured physical activity measures that were slightly improved after controlling for social desirability. Psychosocial variables were strongly associated with self-reports of physical activity, but weakly associated with accelerometer physical activity. Social desirability was positively associated with physical activity preferences (r=0.169) and self-efficacy (r=0.118) and negatively associated (r=-0.158) with self-reported sedentary behavior. Differences in the strength of relationships between self-reported and objectively measured physical activity and psychosocial variables were not a function of social desirability.