The relation of language of instruction and vocabulary to the English spelling of bilingual first graders receiving either English or Spanish literacy instruction and of monolinguals in English literacy instruction was explored. Only bilingual students in Spanish literacy instruction (SLI) exhibited Spanish-influenced spelling, indicating a powerful effect of language of literacy instruction. SLI without English literacy instruction (ELI) may be a prerequisite for the appearance of Spanish influences in English spelling. Spanish-influenced spelling appears to be a normal developmental phenomenon only for those bilingual first graders who have received no ELI. The students in ELI, on average, wrote more orthographically plausible English pseudowords than students in SLI, indicating that the students in SLI simply had not yet learned conventional spelling patterns in English. In addition, children with good Spanish vocabulary showed more Spanish-influenced spelling, while English vocabulary predicted more orthographically plausible English spellings. The relationship between English vocabulary and English spelling was similar for children instructed in Spanish and English. English vocabulary and literacy instruction both made unique, positive contributions to English pseudo-word spelling, while Spanish literacy instruction played a more important role than Spanish vocabulary in the production of Spanish-influenced spelling in English.