Postpartum women have highly disrupted sleep and many experience a disruption in their circadian rhythm during this time. They are also susceptible to mood disruptions during the postpartum period. While mood disruption may be a result of sleep disruption, there are not many data to support a link between circadian rhythm disruption and mood among healthy postpartum women. This study sought to fill that gap. Participants were a convenience sample of 71 women from a larger study. The total sample was 26.4 (SD = 4.0) years old, had a mean annual income of $51,000 (SD = $35,000), and had 15.7 (SD = 2.9) years of education. All women were primiparous (first time mothers), 83.1% were married or cohabitating, 90.1% were white. Data used for these analyses were from postpartum weeks 2 and 12. At each of these weeks, the women were categorized, based on variance across the day on fatigue reports, as having a significant diurnal rhythm or not. Overall, there were no differences in reported mood, stress, or anxiety levels between women with and without a diurnal rhythm at postpartum week 2. However, women with a rhythm at postpartum week 12 reported better mood (p = 0.02, d = 0.62), lower levels of stress (p = 0.03, d = 0.70), and less anxiety (p = 0.02, d = 0.72) than women without a rhythm. In addition, women who were more morning-type were significantly more likely to have a circadian rhythm at both weeks 2 (p = 0.02) and 12 (p = 0.03) postpartum. Women who were older were also more likely to have a significant rhythm, but this difference was only found at week 12 (p = 0.05). The current study furthers knowledge of the benefits of maintaining a circadian rhythm during the postpartum period. It also establishes a novel way of evaluating and perhaps even intervening with women who might be at risk for postpartum mood, stress, or anxiety disorders.