Characteristic affect may influence the development of resilience. Higher levels of resilience may in turn decrease the likelihood of individuals developing symptoms of depression. All first year psychology students (N = 217) were recruited in this longitudinal study to examine whether resilience mediates the relationship between characteristic affect and symptoms of depression. One hundred and seven students completed survey measures at the start of a semester and again 3 months later. Results indicated that greater negative affect predicted worsening of depressive symptoms over 3 months, while greater positive affect predicted a lessening of depressive symptoms over 3 months. Resilience fully mediated the effects of positive affect on change in depression and partly mediated the effects of negative affect on change in depression. These results are interpreted in the context of a hierarchical model of affect and the Broaden and Build Theory, which may explain how resilience arises from positive affect and mediates between affect and symptoms of depression over time.