Stuart Appelbaum, an influential union leader in New York City, was in Tunisia last month, advising the fledgling labor movement there, when he received a flurry of phone calls and e-mails alerting him to the rumblings of something back home. Protesters united under a provocative name, Occupy Wall Street, were gathering in a Lower Manhattan park and raising issues long dear to organized labor.

And gaining attention for it.

Mr. Appelbaum recalled asking a colleague over the phone to find out who was behind Occupy Wall Street — a bunch of hippies or perhaps troublemakers? — and whether the movement might quickly fade.

So far, at least, it has not, and on Wednesday, several prominent unions, struggling to gain traction on their own, made their first effort to join forces with Occupy Wall Street. Thousands of union members marched with the protesters from Foley Square to their encampment in nearby Zuccotti Park.

“The labor movement needs to tap into the energy and learn from them,” Mr. Appelbaum, president of the Retail, Wholesale and Department Store Union, said. “They are reaching a lot of people and exciting a lot of people that the labor movement has been struggling to reach for years.”