This paper investigates whether instruction about phonological correspondences between the native and a closely related language contributes to the intelligibility of this closely related language. Previous research has shown that closely related languages can be mutually intelligible to a certain degree (cf. Gooskens, 2007). Little is known about methods for improving the intelligibility of a closely related language. This paper focuses on improving the intelligibility of spoken Frisian for Dutch speakers. In a 50-minute instruction session, participants got information about the most frequent sound correspondences between Dutch and Frisian, e.g. /sk/ in Frisian is often /sx/ in Dutch. The results of the intelligibility test show no significant improvement, neither at the text level, nor at the word level. Further research could focus on other language combinations, but also on a longer time span of intervention and other linguistic factors, such as unknown vowels.