Screening of behavior problems in young children in pediatric primary care is essential to timely intervention and optimizing trajectories for social-emotional development. Identifying differential behavior problem trajectories provides guidance for tailoring prevention and treatment. To identify trajectories of behavior problems in children 2 to 6 years of age screened in pediatric primary care. This retrospective cohort study identified trajectories of behavior problems and demographic and clinical correlates. Data were collected as part of routine care in 3 pediatric primary care offices and 3 school-based health centers in Ohio serving a primarily low-income population. In total, 15 218 children aged 2 to 6 years with well-child visits between July 13, 2016, and January 31, 2022, were included. Caregivers completed the Strengths and Difficulties Questionnaire (SDQ) at annual well-child visits. Trajectory groups were identified using latent growth mixture modeling of SDQ total difficulties scores, and relative risk ratio (RRR) of various demographic (eg, race) and clinical (eg, depression in caregiver) variables were assessed by multinomial logistic regression analysis. Of 15 281 children (51.3% males), 10 410 (68.1%) were African American or Black, 299 (2.0%) were Asian, 13 (0.1%) were American Indian or Alaska Native, 876 (5.7%) were multiracial, 26 (0.2%) were Native Hawaiian and Other Pacific Islander, 2829 (18.5%) were White, and 39 (0.02%) were categorized as other. In addition, 944 (6.2%) identified as Hispanic and 14 246 (93.2%) as non-Hispanic. Four behavior problem trajectory groups reflecting severity were identified: low-stable (LS; 10 096 [66.1%]), moderate-decreasing (MD; 16.6%), low-increasing (LI; 13.1%), and high-increasing (HI; 4.3%). Relative to the LS group, patients in each elevated group were more likely to be male (HI RRR, 1.87 [95% CI, 1.55-2.26]; MD RRR, 1.55 [95% CI, 1.41-1.71]; and LI RRR, 1.94 [95% CI, 1.70-2.21]), White (HI RRR, 2.27 [95% CI, 1.83-2.81]; MD RRR, 1.28 [95% CI, 1.13-1.45]; and LI RRR, 1.54, [95% CI, 1.32-1.81]), publicly insured (HI RRR, 0.49 [95% CI, 0.28-0.84]; MD RRR, 0.56 [95% CI, 0.43-0.73]; and LI RRR, 0.50 [95% CI, 0.35-0.73]), have a social need (HI RRR, 3.07 [95% CI, 2.53-3.73]; MD RRR, 2.02 [95% CI, 1.82-2.25]; and LI RRR, 2.12 [95% CI, 1.84-2.44]), and have a caregiver with depression (HI RRR, 1.66 [95% CI, 1.38-2.00]; MD RRR, 1.44 [95% CI, 1.31-1.58]; and LI RRR, 1.39 [95% CI, 1.23-1.58]). Relative to the LI group, patients in the MD group were less likely to be male (RRR, 0.80; 95% CI, 0.68-0.93). The substantial portion of young children with increased behavior problems observed in this cohort study underscores the need for screening in pediatric primary care. Caregivers with depression and family social needs warrant prioritization in early prevention and treatment to alter elevated trajectories.