This article examines how compulsive Internet use and marital well-being are related to each other. We suggest that they are negatively related and explore whether compulsive Internet use predicts marital well-being or vice versa. The relation between compulsive Internet use and marital well-being is tested in a two-wave prospective study among 190 newlywed couples. The results suggest that (a) compulsive Internet use predicts marital well-being, and not vice versa, (b) that this is a within- rather than a cross-partner effect, and (c) that the frequency of Internet use may be positively related to marital well-being. The results are discussed in terms of the mechanisms that underlie the link between compulsive Internet use and relationship quality. © 2011 International Communication Association.