This study investigates the effect of morphosyntactic differences on our ability to comprehend a closely related language. Previous studies of mutual intelligibility, or receptive bilingualism, have focussed largely on the role of extra-linguistic, lexical, or phonetic factors. Although there is reason to believe that differences in morphology and syntax might worsen the ability to comprehend a closely related linguistic variety, this claim is previously untested. This article reports an experimental investigation of whether Danes’ comprehension of the closely related language Norwegian is impeded by certain Norwegian grammatical constructions. We tested sentence comprehension experimentally in four different conditions to assess the relative effect of non-native morphosyntactic features as opposed to non-native phonology on intelligibility. Correctness rates of the responses and reaction times were measured. Results indicate that word-order differences cause larger problems for listeners than morphological differences. However, the non-native phonology featured in the experiment impedes comprehension to a larger degree than the morphosyntactic differences do. Our results have implications for work in natural language processing as well as for studies in speech comprehension, particularly those applied to situations of language learning and teaching in areas where receptive bilingualism is widespread.