Leonard A. Wilf, born in 1947 in Göggingen, Allied-occupied Germany, to Holocaust survivors Harry Wilf and Judith Wilf (d. 2006), immigrated to the United States with his family. From age nine, he grew up in Hillside, New Jersey, next door to his cousin Zygi Wilf. He earned a Bachelor of Arts degree cum laude from Boston University, a Juris Doctor from Georgetown University Law Center (where he served as editor of the Georgetown Law Journal), and a Master of Laws in taxation from New York University School of Law in 1977. Wilf joined the family real estate business, Garden Homes Development, serving as its president; the company is headquartered in Short Hills, New Jersey, and has been involved in various developments. The family has faced legal disputes, including a 2013 New Jersey Superior Court ruling finding Wilf family members guilty of defrauding business partners in a Morristown case. The Wilf family's net worth was estimated at $5 billion in 2015.

Wilf is a family member and cousin of Mark Wilf, who serves as president of the Minnesota Vikings. He is a co-owner and vice chairman of the NFL's Minnesota Vikings alongside cousins Zygi Wilf (chairman) and Mark Wilf. He was also a co-owner of Major League Soccer's Nashville SC starting in 2017.

Personally, Wilf was married to philanthropist Dr. Marcia Robbins-Wilf (daughter of toy company co-founder Saul Robbins), but the divorce took 12 years and cost $20 million in legal fees. He is now married to Beth Wilf and has four children, including Orin Wilf. An active philanthropist focused on Holocaust remembrance and healthcare, he formerly chaired the American Society for Yad Vashem, serves on the U.S. Holocaust Memorial Museum's council, and has been on the board of NewYork-Presbyterian Hospital since 2009. He resides in New York City.