This study investigates the within- and cross-language relationships between orthographic processing and spelling in children learning to read in languages that share the same Roman script: namely, English and French. These relationships were examined in a group of 152 Grade 1 children attending a Canadian French immersion program. Measures of English and French orthographic processing and standardized measures of English and French spelling were administered, in addition to non-verbal ability, phonological awareness, and English and French word reading. We found a within-language relationship between orthographic processing and spelling in each of English and French. Cross-language transfer from French orthographic processing to English spelling was also observed. The results suggest that orthographic processing is important for spelling development within English and French and across the two languages in French immersion children.