This article examines what assimilation trajectories were manifest among present-day Mediterranean Muslims and pre–World War II Jews in Dutch society. Alba and Nee conceptualized assimilation in terms of processes of spanning and altering group boundaries, distinguishing between boundary crossing, blurring, and shifting. This study carves out to what extent assimilation processes like boundary crossing, shifting, and blurring had taken place for those two non-Christian minority groups in Dutch society. This research is based on findings of recent (quantitative) empirical research into the assimilation of pre–World War II Jews in the Netherlands and on the collection of comparable research and data for the assimilation of contemporary Mediterranean Muslims. Our study suggests that processes of boundary crossing, such as observance of religious practices and consumption of religious food, and blurring, such as intermarriage, residential segregation, and religious affiliation, are much less advanced for Mediterranean Muslims in the present time. Though several factors might account for differences in boundary-altering processes between pre–World War II Jews and contemporary Mediterranean Muslims such as differences in length of stay in the Netherlands, the secularization process, and globalization, Jewish assimilation might provide us some reflections on assimilation of Mediterranean Muslims. The continuous arrival of Muslim newcomers might affect attitudes and behavior of settled Mediterranean Muslims, while policy to restrict family migration might be insufficient to stimulate Muslims to integrate in Dutch society given the quite negative mutual perceptions, the slow process of residential spreading, the continuation of observance of religious practices, and the low intermarriage rate.