This research aims to identify factors associated with marital instability among Jewish and mixed (Jewish and non-Jewish) couples following immigration from the former Soviet Union. Based on the Strangeness Theory and the Model of Acculturation, we predicted that non-Jewish immigrants would be less well adjusted personally and socially to Israeli society than Jewish immigrants and that endogamous Jewish couples would have better interpersonal congruence than mixed couples in terms of personal and social adjustment. The sample included 92 Jewish couples and 92 ethnically-mixed couples, of which 82 couples (40 Jewish, 42 mixed) divorced or separated after immigration and 102 couples (52 Jewish, 50 ethnically mixed) remained married. Significant differences were found between Jewish and non-Jewish immigrants in personal adjustment, and between endogamous and ethnically-mixed couples in the congruence between spouses in their personal and social adjustment. Marital instability was best explained by interpersonal disparity in cultural identity and in adjustment to life in Israel. The findings expand the knowledge on marital outcomes of immigration, in general, and immigration of mixed marriages, in particular.