Behavioral theory posits that certain environmental changes and avoidant behaviors inhibit individuals from experiencing environmental reward and reinforcement and subsequently leads to the development and maintenance of depressive symptoms. Using self-report and behavioral (daily diary) indices of environmental reward as proxy measures for positive reinforcement, this investigation examined whether environmental reward mediated the relationship between avoidance and depression. When controlling for anxiety, both indices of environmental reward significantly mediated the relationships of depression with cognitive, behavioral and total avoidance. Post-hoc mediation analyses were conducted to examine potential gender differences. Self-reported environmental reward significantly mediated the relationship between avoidance and depression across both genders. Among females, however, daily diary-measured reward only mediated the relation between cognitive avoidance and depression. In males daily diary reward was a mediator with all three forms of avoidance and depression. This investigation provides initial support for reinforcement as a significant mediator between avoidance and depression and further highlights the relevance of avoidance and reinforcement in behavioral conceptualizations of depression.