Background: Young children are often required to carry out writing tasks in an educational context. However, little is known about the patterns of writing skills that children with specific language impairment (CwSLI) have relative to their typically developing peers. Aims: To assess the written language skills of CwSLI and compare these with typically developing peers. It also aimed to assess the relative contributions of reading and spelling skills to written language skills. Methods & Procedures: Forty-five children took part in the study: 15 were CwSLI, 15 were a chronological age match and 15 were a spelling age match. The children took part in a range of tasks that assessed writing, reading and spelling abilities. Outcomes & Results: In their written language and compared with typical age-matched peers, CwSLI used a significantly less diverse range of words, had lower quality written compositions overall, and lower levels of organization, unity and coherence. They also had a higher proportion of spelling errors. Overall, writing skills were strongly associated with reading skills. Conclusions & Implications: The findings demonstrate the challenges CwSLI have in producing good-quality written text and that these challenges are likely to be related to the linguistic skills profile shown by these children. (Contains 3 tables.)