We examine morphosyntactic knowledge of Labrador Inuttitut by Inuit receptive bilinguals (RBs) – heritage speakers who are capable of comprehension, but produce little or no speech. A grammaticality judgment study suggests that RBs possess sensitivity to morphosyntactic violations, though to a lesser degree than fluent bilinguals. Low-proficiency RBs are sensitive only to the most basic grammatical properties. Case omission is most difficult to detect, but morphemes bearing incorrect features (case oversuppliance, number agreement mismatch) or ordered incorrectly (tense and agreement, tense and negation) are easier, and performance on incorrect ordering of morphemes is near target with the core agreement morpheme for all RBs. While receptive bilinguals show patterns of grammatical deficits, they also demonstrate clear knowledge of the basic properties of word structure in Inuttitut. This has implications both for the psycholinguistics of bilingualism and for language revitalization efforts.