Background An association between children’s early language development and their emotional and behavioural functioning is reported in the literature. The nature of the association remains unclear and it has not been established if such an association is found in a population-based cohort in addition to clinical populations. Methods This study examines the reported association between language development and emotional and behavioural functioning in a population-based cohort. Data from 1,314 children in the Children in Focus (CiF) sample from the Avon Longitudinal Study of Parents and Children (ALSPAC) were analysed. Regression models identified the extent to which early language ability at 2 years of age and later language ability at 4 years of age is associated with emotional and behavioural functioning at 6 years while accounting for biological and social risk and adjusting for age and performance intelligence (PIQ). Results A series of univariable and multivariable analyses identified a strong influence of biological risk, social risk and early and later language ability to emotional and behavioural functioning. Interestingly, social risk dropped out of the multivariate analyses when age and PIQ were controlled for. Early expressive vocabulary at 2 years and receptive language at 4 years made a strong contribution to emotional and behavioural functioning at 6 years in addition to biological risk. The final model accounted for 11.6% of the variance in emotional and behavioural functioning at 6 years. Conclusions The study identified that early language ability at 2 years, specifically expressive vocabulary and later receptive language at 4 years both made a moderate, but important contribution to emotional and behavioural functioning at 6 years of age. Although children’s language development is important in understanding children’s emotional and behavioural functioning, the study shows that it is one of many developmental factors involved.