Orthographic and linguistic knowledge are known predictors of reading and writing, yet little research with adolescent readers explores how such knowledge predicts reading and writing in a single model. We worked with 583 adolescent readers in remedial reading classes in grades 6-8 to collect indicators of orthographic and linguistic knowledge as well as reading comprehension and written expression. Using structural equation modeling, we examined how orthography and language predicted reading and writing and whether reading predicted writing and vice versa. We found that morphology, syntax, and orthography all independently predicted reading and writing, but linguistic knowledge was more strongly associated with reading than writing. Writing and reading did not differ in their effects on one another. Results extend theory on the relationship between language, reading, and writing and add to the research base on adolescent readers with implications for curriculum and instruction.