For children with dyslexia, learning to write constitutes a great challenge. There has been consensus that the explanation for these learners' delay is related to a phonological deficit. Results from studies designed to describe dyslexic children's spelling errors are not always as clear concerning the role of phonological processes as those found in reading studies. In irregular languages like French, spelling abilities involve other processes than phonological processes. The main goal of this study was to describe the relative contribution of these other processes in dyslexic children's spelling ability. In total, 32 francophone dyslexic children with a mean age of 11.4 years were compared with 24 reading‐age matched controls (RA) and 24 chronological‐age matched controls (CA). All had to write a text that was analysed at the graphemic level. All errors were classified as either phonological, morphological, visual‐orthographic or lexical. Results indicated that dyslexic children's spelling ability lagged behind not only that of the CA group but also of the RA group. Because the majority of errors, in all groups, could not be explained by inefficiency of phonological processing, the importance of visual knowledge/processes will be discussed as a complementary explanation of dyslexic children's delay in writing. Copyright © 2016 John Wiley & Sons, Ltd.