A body of empirical research has revealed that there are associations among language skills, peer interactions, and behavioral problems in childhood. At the same time, however, there has been comparatively less research devoted to exploring the mutual unfolding of these factors over the first few years of life. The current study is designed to partially address this gap in the literature by examining how language skills, negative peer interactions, and behavioral problems are interrelated in a sample of twins drawn from the Early Childhood Longitudinal Study-Birth Cohort (ECLS-B). Employing a quantitative genetic framework, the results of the current study revealed that variance in language skills, negative peer interactions, and externalizing behavioral problems were all due to a combination of genetic and environmental factors. Bivariate Cholesky models indicated that most of the covariance among language skills, negative peer interactions, and externalizing behavioral problems was due to common genetic factors. Additional analyses using a modified DeFries-Fulker approach nested within a path model revealed a bidirectional association between negative peer interactions and externalizing behavioral problems, wherein there appeared to be feedback loops between the two. Implications of the results are discussed and avenues for future research are offered.