The present study examined the relations of children's effortful control (EC), emotion understanding, maladjustment, social competence, and relationship quality with nonparental caregivers in a sample of 30-, 42-, and 54-month olds. EC was measured with mothers' and caregivers' reports, as well as observed behavioral tasks. Emotion understanding was assessed by asking children to identify emotions during a puppet task. Mothers and caregivers also reported on children's problem behaviors and social competence. Caregivers provided reports of the quality of their relationship with children. Results from longitudinal structural equation models indicated that even after controlling for sex, SES, language ability, and previous levels of constructs, emotion understanding predicted EC one year later at 42 and 54 months. In addition, children with higher EC had more positive relationships with caregivers at 42 and 54 months. Although EC and EU were not significantly related to maladjustment and social competence after accounting for within time covariation among constructs and longitudinal stability, marginal findings were in expected directions and suggested that more regulated children with better emotion understanding skills had fewer behavioral problems and were more socially skilled. Findings are discussed in terms of the strengths and limitations of the present study.