Objective: Distinctive stressors facing pregnant and postpartum individuals during the COVID-19 pandemic may have affected their emergency department (ED) care-seeking for behavioral health concerns and violence victimization. We tested whether the incidence of postpartum behavioral health and assault injury ED visits differed for individuals according to their months of postpartum pandemic exposure. Methods: We used statewide, longitudinally linked hospital and ED administrative claims data from California to classify all individuals with hospital deliveries between January 1, 2016, and December 31, 2020, according to their months of postpartum pandemic exposure. Outcomes comprised 12-month incidence of any ED visit for a psychiatric disorder, drug use disorder/overdose, alcohol use disorder/intoxication, or assault injury, defined using International Classification of Diseases-Clinical Modification, version 10 codes. Risk ratios compared the incidence of each outcome among people with 1-12 months of postpartum pandemic exposure to those with 0 months of exposure. Results: Compared to people with 0 months of postpartum pandemic exposure (n = 1,163,215), delivering people with 1-12 month' exposure (range: n = 26,836 to n = 273,561) were approximately equally likely to have a postpartum ED visit for a psychiatric disorder, drug use disorder, or alcohol use disorder, after adjusting for demographic differences (most p > 0.10). The incidence of assault injury was significantly lower among delivering individuals with 11 or 12 months of pandemic exposure (RRadj = 0.70 and 0.91, respectively; both p < 0.01) compared to those with 0 months. Conclusions: Contrary to expectations, the pandemic did not appear to have affected ED utilization for most behavioral health conditions among postpartum individuals, but assault injury ED visits declined.