The purpose of this study is to examine the efficacy of exercise and wellness/support interventions for preventing postpartum depression. Specifically, 450 sedentary postpartum women (2-6 weeks postpartum) with a history of depression prior to pregnancy will be randomized to one of three groups each lasting six months: (1) telephone-based exercise intervention; (2) telephone-based wellness/support intervention; or (3) usual care. Participants will also complete a follow-up assessment session at 9 months. Participants will be recruited via online, email, and print advertisements. The investigators will obtain healthcare provider consent for each participant prior to randomization. The exercise intervention will consist of a theory-based telephone intervention shown to increase exercise among postpartum women in a previous study (Lewis et al., 2011). The wellness/support condition will be on the same schedule as the exercise intervention and will address several topics related to wellness. The usual care condition will receive their choice of the exercise or wellness/support condition upon completion of their final assessment. The primary dependent variable will be depression as measured by the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I) and the Edinburgh Postnatal Depression Scale (EPDS). Exercise adherence will be assessed using the 7-Day Physical Activity Recall Interview and the ActiGraph (i.e., an accelerometer, an objective measure of exercise).