Parents have experienced considerable challenges and stress during the COVID‐19 pandemic, which may impact their well‐being. This meta‐analysis sought to identify: (1) the prevalence of depression and anxiety in parents of young children (<age 5) during the COVID‐19 pandemic, and (2) sociodemographic (e.g., parent age, being racially minoritized) and methodological moderators (e.g., study quality) that explain heterogeneity among studies. A systematic search was conducted across four databases from January 1, 2020 to March 3, 2021. A total of 18 non‐overlapping studies (8981 participants), all focused on maternal mental health, met inclusion criteria. Random‐effect meta‐analyses were conducted. Pooled prevalence estimates for clinically significant depression and anxiety symptoms for mothers of young children during the COVID‐19 pandemic were 26.9% (95% CI: 21.3–33.4) and 41.9% (95% CI: 26.7–58.8), respectively. Prevalence of clinically elevated depression and anxiety symptoms were higher in Europe and North America and among older mothers. Clinically elevated depressive symptoms were lower in studies with a higher percentage of individuals who were racially minoritized. In comparison, clinically elevated anxiety symptoms were higher among studies of low study quality and in samples with highly educated mothers. Policies and resources targeting improvements in maternal mental health are essential.