Limited information is available about the rates and risk correlates of socioemotional/behavioral problems in young children in pediatric primary care settings serving low-income families. Our objective was to determine rates of clinically significant socioemotional/behavior problems in 12- to 48-month-olds from low-income families and identify associations between problems and individual and cumulative demographic and psychosocial risks. In this study, 378 Spanish- and English-speaking mothers attending a pediatric primary care practice serving low-income families were surveyed before well-child visits to assess socioemotional/behavioral problems (Brief Infant-Toddler Social-Emotional Assessment; M.J. Briggs-Gowan & A.S. Carter, ) and psychosocial and demographic risks (e.g., unemployment, low social support) (Parent Risk Questionnaire; D.I. Lowell, A.S. Carter, L. Godoy, B. Paulicin, & M.J. Briggs-Gowan, ). We found that 19.8% of children had clinically significant problems, and 53.2% experienced one or more psychosocial risks. Clinically significant socioemotional/behavioral problems were modestly to strongly associated with individual psychosocial risks, with the strongest associations with parental medical problems, parent depression/anxiety, and extreme parental distress, Adjusted Relative Risk (ARR) = 4.8-6.6, p < .0001. Cumulative demographic and psychosocial risk were uniquely associated with clinically significant problems, particularly among children experiencing three to four psychosocial risks, ARR = 3.0-11.6, p < .05. Psychosocial risks affect the majority of low-income families with young children, with a steep increase in likelihood of clinically significant socioemotional/behavioral problems as risks accumulate, underscoring the need to address both socioemotional/behavioral issues and psychosocial risk in young children.