Objectives: Research shows that physical activity during postpartum affects maternal physical and mental health. In this study, we examined the associations of a phone-based physical activity intervention on objectively measured physical activity and self-reported fatigue. Methods: Participants (N=450) were randomly assigned to either a phone-based physical activity group (N=150), a wellness group (N=150), or a control group (N=150). Participants were on average 4.35 weeks postpartum at the time of the study. Physical activity was measured via accelerometer, and fatigue was measured via self-reported survey. We used a series of one-way analyses of variance (ANOVAs) to examine differences between study groups at the 6-month timepoint. Results: The physical activity group was significantly more active than the control group at 6 months, F(2, 243) = 4.27, p < .05. The control group had significantly higher levels of reduced motivation at 6 months F(2,372) = 3.534, p < .05. Other subscales of the fatigue measure were not significantly different by group. Conclusions: Phone-based counseling may be a useful tool to increase physical activity among postpartum women, but more research is needed to see if those benefits are sustained.