Background: Specific language impairment (SLI) is diagnosed when a child shows isolated structural language problems. The diagnosis of pragmatic language impairment (PLI) is given to children who show difficulties with the use of language in context. Unlike children with SLI, these children tend to show relatively intact structural language skills while they do exhibit clear communicative deficits. There is hardly any research on the relationship between pragmatic competence and behavioural problems. Existing research suggests a strong relationship, but has only been executed on clinical SLI samples. Moreover, it is not known whether pragmatic language problems are related to specific types of behavioural problems. Aims: This study aims to clarify the incidence and nature of behavioural problems in children with PLI using a prognostic design in mainstream education. This design should provide valuable insights into the general relationship between PLI and various behavioural problems. Methods & Procedures: Teachers completed the Children's Communication Checklist (CCC) and the Strengths and Difficulties Questionnaire (SDQ) and provided additional data for a sample of 1364 children aged 4 years. Outcomes & Results: Within the community sample, pragmatic competence is highly correlated with behavioural problems. Pragmatic competence is a good predictor of behavioural problems, and once pragmatic competence is accounted for, structural language abilities do not predict behavioural problems. Children with pragmatic language impairment often show behavioural problems, largely of an externalizing nature. The most prominent problems are hyperactivity and the lack of prosocial behaviour, which reach clinical levels for this group. However, all problem levels are elevated compared with normally developing children. Conclusions & Implications: Young children with PLI show a wide variety of behavioural problems. Early assessment of pragmatic competence may benefit early detection of children at risk of behavioural problems. Furthermore, due to the relationship between pragmatic competence, behavioural problems and possible underlying disorders such as autism and attention-deficit hyperactivity disorder (ADHD), early assessment of pragmatic competence may also provide an early marker for the detection of autism or ADHD. (Contains 5 tables and 1 figure.)