Public health restrictions to protect physical health during the COVID-19 pandemic had unintended effects on mental health, which may have disproportionately affected some potentially vulnerable groups. This scoping review of qualitative research provides a narrative synthesis of new mothers' perspectives on their mental health during COVID-19 pandemic restrictions through pregnancy to the postpartum period. Database searches in PubMed, CINAHL, and PsycINFO sought primary research studies published until February 2023, which focused on new mothers' self-perceived mental health during the pandemic (N = 55). Our synthesis found that new mothers' mental health was impacted by general public health restrictions resulting in isolation from family and friends, a lack of community support, and impacts on the immediate family. However, public health restrictions specific to maternal and infant healthcare were most often found to negatively impact maternal mental health, namely, hospital policies prohibiting the presence of birthing partners and in-person care for their infants. This review of qualitative research adds depth to previous reviews that have solely examined the quantitative associations between COVID-19 public health restrictions and new mothers' mental health. Here, our review demonstrates the array of adverse impacts of COVID-19 public health restrictions on new mothers' mental health throughout pregnancy into the postpartum period, as reported by new mothers. These findings may be beneficial for policy makers in future public health emergency planning when evaluating the impacts and unintended consequences of public health restrictions on new mothers.