COVID-19-related stressors – including social distancing, material hardship, increased intimate partner violence, and loss of childcare, among others – may result in a higher prevalence of depression among postpartum individuals. This study examines trends in postpartum depression in the US from 2018 to 2022, as well as correlates of treatment choices among women with postpartum depression. 1,108,874 women aged 14-64 in the Komodo Healthcare Map with 1+ live birth between April 2018 and December 2021 and had continuous enrollment 2+ years before and 4+ months after the delivery date were included. Prevalence of depression during postpartum (within 3 months after delivery) was calculated before (April 2018–March 2020) and during (April 2020–March 2022) COVID-19. Multinomial logistic regression was used to investigate correlates of treatment choices (no treatment, medication-only, psychotherapy-only, or both). The prevalence of postpartum depression increased from 9.7% pre-pandemic to 12.0% during the pandemic (p < 0.001). Among 119,788 women with postpartum depression in 2018-2022, 47.0% received no treatment, 35.0% received medication-only, 10.0% received psychotherapy-only, and 7.4% received both within one month following their first depression diagnosis. Factors associated with an increase in the odds of receiving medication-psychotherapy treatment (vs. no treatment) included older ages; commercial insurance coverage; lower social vulnerability index; history of anxiety or mood disorder during and before pregnancy; and being diagnosed by a nurse practitioner, physician assistant, or behavioral care practitioner (vs. physician). Similar patterns were observed for medication-only and psychotherapy-only treatments. In this large, nationally representative sample of US insured population, the prevalence of postpartum depression increased significantly by 2.3 percentage-points during the pandemic (or a relative increase of 23.7%). Nonetheless, almost half of women with postpartum depression received no treatment, and only 7.5% received both medication and psychotherapy. The study highlighted potential socioeconomic and provider variation in postpartum depression treatment.