This study investigated which components of the writing production process are impaired in Spanish children with developmental dyslexia (DD) aged 8 to 12 years. Children with and without dyslexia (n = 60) were assessed in their use of the lexical and the sublexical routes of spelling as well as the orthographic working memory system by manipulating lexical frequency, phonology-to-orthography (P-O) consistency, and word length in a copying task and a spelling-to-dictation task. Results revealed that children with dyslexia produced longer written latencies than chronological age-matched (CA) controls, more errors than CA and reading age-matched (RA) controls, and writing durations similar to CA controls. Latencies were more affected by frequency, consistency, and length in the DD group and the RA group than in CA controls. Children in the DD and RA groups produced longer written latencies in the copying than in the spelling-to-dictation task, while controls in the CA group were not affected by the task. Results indicate that spelling impairments in Spanish children with dyslexia affect the relative involvement of lexical and sublexical information during handwriting. Meanwhile, effects on writing speed seem to be related to deficits in reading ability, and accuracy scores seem to be poorer than expected by children's reading skill.