Socioeconomic status (SES) at different points in a child’s lifetime may have different effects on health outcomes. This study aimed to examine longitudinal associations between SES and psychosocial problems in preschool children (n = 2509, Mage = 24.2 ± 1.3 months). The psychosocial problems of children were assessed using the Brief Infant–Toddler Social and Emotional Assessment at age 2 years and age 3 years and categorized as having yes/no psychosocial problems. Four groups of pattern of presence/absence of psychosocial problems between age 2 and 3 years were classified: (1) ‘no problems’, (2) ‘problems at age two’, (3) ‘problems at age three’, and (4) ‘continuing problems’. Five indicators of SES (i.e., maternal education level, single-parent family, unemployment, financial problems, and neighborhood SES) were evaluated. Results showed around one-fifth (2Y = 20.0%, 3Y = 16.0%) of children had psychosocial problems. Multinomial logistic regression models revealed low and middle maternal education levels were associated with ‘problems at age two’; low maternal education level and financial problems were associated with ‘problems at age three’; low and middle maternal education level, single-parent family, and unemployment were associated with ‘continuing problems’. No associations were observed between neighborhood SES and any pattern. Results suggest children in a lower SES, indicated by maternal education, single-parent family, and financial stress, had higher odds of developing and continuously having psychosocial problems in early childhood. These findings call for optimally timing interventions to reduce the impact of disadvantaged SES in early childhood on psychosocial health.