The Crémieux Decree, which was promulgated on September 24 1870, is a key moment in the history of the Jews of Algeria because it recognized them collectively as French citizens. It was thought to be an answer to the failure of the previous legislation, the 1865 senatus-consulte which defined the status of natives, both Muslims or Jews as “French without citizenship,” but allowed individuals from these groups to ask for citizenship through naturalization, which only a very few did. The historiography has therefore neglected the Jewish dimension of the naturalizations that occurred in Algeria. However, the Crémieux Decree did not concern all the Algerian Jews. In particular, the Jews from the M’zab, conquered in 1882, and even more importantly, Tunisian and Moroccan migrant Jews were excluded from this assimilation. As this article demonstrates, however, the study and analysis of the naturalization of these Jews is extremely instructive, and demonstrates the diversity of the Algerian Jewish population under French rule.