After receiving his pension, he became a propagandist, in 1899.
for the Alliance, and later for early Zionism.
Nissim Behar can be seen as the founder of modern Hebrew language education, largely because Eliezer Ben Yehuda taught Hebrew using the new "direct method".
Behar was a strong advocate of the direct method, which prevailed in the further development of Hebrew language education in the framework of the "ulpan" system, that led to the success of Hebrew revival.
In 1901, Behar moved to New York City, where he directed the National Liberal Immigration League (1906 to 1924), to lobby against anti-immigration legislation in the United States.
The League was a constant irritation for Louis Marshall of the American Jewish Committee, because it made no effort to hide its Jewish identity in its high-profile activities against restricting immigration.
Marshall and the AJC, while similarly opposed to restrictions, felt any public Jewish role would undermine their lobbying campaign and provoke anti-Semitism; the AJC refrained from such public activities on the issue, and Marshall's work was usually confined to behind-the-scenes contacts with individual members of Congress.
Behar was an enthusiastic propagandist for the Zionist idea; he called for the return of the Kotel Hamaaravi, the Wailing Wall, to Jewish hands.