The solemn boulevards and quiet side streets of the 17th Arrondissement in Paris suggest Jewish life in France is vibrant: There is a new profusion of kosher groceries and restaurants, and about 15 synagogues, up from only a handful two decades ago.

But for residents like Joanna Galilli, this area in northwestern Paris represents a tactical retreat. It has become a haven for many Jews who say they have faced harassment in areas with growing Muslim populations. Ms. Galilli, 28, moved to the neighborhood this year from a Parisian suburb where “anti-Semitism is pretty high,” she said, “and you feel it enormously.”

“They spit when I walked in the street,” she said, describing reactions when she wore a Star of David.

France has a painful history of anti-Semitism, with its worst hours coming in the 1930s and during the German occupation in World War II. But in recent months, an impassioned debate has erupted over what commentators are calling the “new anti-Semitism,” as Jewish groups and academic researchers trace a wave of anti-Semitic acts to France’s growing Muslim population.