The foundation created by the late hotel mogul Leona Helmsley plans to announce today that John R. Ettinger, a lawyer, will serve as its new leader.

Mr. Ettinger joins the philanthropy after 32 years at Davis Polk & Wardwell, a global law firm. This spring, he stepped down as the firm’s managing partner.

The Leona M. and Harry B. Helmsley Charitable Trust now holds roughly $4-billion in assets, making it one of the country’s biggest philanthropies. The New York foundation will grow even wealthier as it receives additional money from the estate of Ms. Helmsley, who died in 2007.

Since her death, the trust has faced legal challenges from animal-welfare groups, which contend that the fund is ignoring Ms. Helmsley’s wish that much of her money go to help dogs. The trust currently supports charities working in education, the environment, health, and human services.

While pursuing his legal career, Mr. Ettinger served on the boards of several nonprofits, including Communities in Schools, a national group that encourages youths to stay in school. He holds a bachelor’s degree from Yale University and a law degree from Harvard.