Many children with autism spectrum disorders (ASD) have reading comprehension difficulties, but the level of processing at which comprehension is most vulnerable and the influence of language phenotype on comprehension skill is currently unclear. We explored comprehension at sentence and passage levels across language phenotypes. Children with ASD and age-appropriate language skills (n = 25) demonstrated similar syntactic and semantic facilitation to typically developing peers. In contrast, few children with ASD and language impairments (n = 25) could read beyond the single word level. Those who could read sentences benefited from semantic coherence, but were less sensitive to syntactic coherence. At the passage level, the strongest predictor of comprehension was vocabulary knowledge. This emphasizes that the intimate relationship between language competence and both decoding skill and comprehension is evident at the sentence, as well as the passage level, for children with ASD.