Background and AimsSocial‐emotional delays and behavioral problems at preschool age are associated with negative outcomes at school age, including ongoing behavior problems, poorer social functioning, and academic difficulties. Understanding modifiable risk factors for suboptimal development requires consideration of contemporary family circumstances to determine areas for effective early intervention to optimize development. This study aimed to identify risk factors for delayed social‐emotional development and behavior problems at age two among participants of the All Our Babies/Families cohort study.MethodsMothers (N = 1596) completed five comprehensive questionnaires spanning midpregnancy to 2 years postpartum. At child age two, behavior and competence outcomes were measured using the Brief Infant‐Toddler Social and Emotional Assessment. Chi square analysis and multivariable logistic regression modeling was used to identify key risk factors for suboptimal child outcomes. Predicted probabilities for adverse outcomes in the presence of risk were calculated.ResultsRisk factors for possible delayed social‐emotional development in children included maternal depression at 2 years postpartum (OR 2.46, 95% CI 1.63, 3.72), lower parenting self‐efficacy at 2 years postpartum (OR 2.76, 95% CI 1.51, 5.06), non‐daily play‐based interaction when child was 1 and 2 years old (OR 1.43, 95% CI 1.02, 1.99), child delayed sleep initiation at 2 years of age (OR 1.58, 95% CI 1.05, 2.37), and playgroup non‐attendance between 1 and 2 years postpartum (OR 1.43, 95% CI 1.03, 1.99). Risk factors for possible behavior problems included lower maternal optimism during pregnancy (OR 2.02, 95% CI 1.36, 2.99), maternal depression at 2 years postpartum (OR 2.19, 95% CI 1.46, 3.27), difficulty balancing responsibilities at 2 years postpartum (OR 2.32 95% CI 1.55, 3.47), child second language exposure at 2 years of age (OR 1.88, 95% CI 1.37, 2.58), child delayed sleep initiation at 2 years of age (OR 1.55 95% CI 1.06, 2.26), child frequent night wakings at 2 years of age (OR 2.95 95% CI 2.13, 4.10), and more screentime exposure at 2 years of age (OR 1.85 95% CI 1.34, 2.54).ConclusionsThis study suggests that addressing maternal mental health and promoting parenting strategies that encourage play‐based interaction, limiting screen time, preventing sleep problems, and engagement in informal playgroups would reduce the risk of behavior and social‐emotional problems.