The present study examined longitudinal associations between behavioral self-regulation and social-emotional functioning across four waves of measurement during the transition from preschool to kindergarten in a low-income sample. Participants included two cohorts of children (N = 558; 51% male). Children in both cohorts were 4 years old (Cohort 1: M = 4.82 years, SD = .31; Cohort 2: M = 4.80 years, SD = .31). Forty-four percent of children were Black, 32% were White, 13% were Latino, 10% were Multiracial, and 1% were Asian. Monthly income ranged from $0-5,539 (M = $1,508.18, SD = $892.92). Two statistical methods were used to examine relations among constructs. The cross-lagged panel model revealed a mixed pattern of relations between behavioral self-regulation and two indicators of social-emotional functioning (social skills and behavior problems) over time. There were no significant relations among behavioral self-regulation and social-emotional functioning during the preschool year; however, evidence for bidirectional associations were found between the spring of preschool and the fall of kindergarten. There were no significant relations among behavioral self-regulation and behavior problems at any time point. Finally, there were bidirectional relations among social skills and behavior problems in preschool, but directional relations emerged after this time point. A second model that included random intercepts was also run with the cross-lagged paths. Results from this model indicated that the random intercepts between behavioral self-regulation, social skills, and behavior problems were significantly related. Implications for future research are discussed. (PsycInfo Database Record (c) 2021 APA, all rights reserved).