--- - |2 Abstract The menstrual cycle impacts mood and neural response to reward—phenomena that may be related to natural fluctuations in ovarian hormones. Using a within‐subject design, the present study examined ovarian hormones (i.e., estradiol and progesterone) and ERPs in response to feedback indicating gains and losses in both the follicular and luteal phases of the menstrual cycle. We examined whether hormone levels and variation in neural response to reward and loss across menstrual cycle phases were associated with depressive symptoms. Participants high in depressive symptoms showed a reduced reward positivity (RewP) to monetary gains during the luteal phase of the menstrual cycle as compared to the follicular phase, while those low in depressive symptoms showed no change in the RewP to monetary gains between phases. Thus, increased fluctuation in the neural response to gains (but not losses) across menstrual cycle phases was associated with greater depression symptoms. Overall, findings indicate that hormonal fluctuations associated with the menstrual cycle may relate to depressive symptoms by altering reward sensitivity. Furthermore, fluctuation in the neural response to rewards over the menstrual cycle may play an important role in the expression of depressive symptoms. - Psychophysiology, EarlyView.