Greenleaf suffered from appendicitis, and had his appendix removed on April 3, 1933. He never recovered from the shock of the surgery, and died in Stamford Hospital in Stamford, Connecticut, on April 15. Funeral services were held at the Congregational Church in New Canaan, and he was buried at the New Cemetery in Somerville, New Jersey. Greenleaf married Bertha Potts of New York City on June 14, 1899. She was the daughter of George A.H. and Helen (Hard) Potts, whose wealthy mining family founded Pottsville, Pennsylvania. They had a son, Donald Leal Greenleaf, born June 5, 1890. Bertha Potts Greenleaf died in 1911. Greenleaf was a Republican, but not active in party politics. He was a member of the Columbia University Club, the Cosmos Club, and the Century Club. He was an associate of the National Academy of Design, and served several times on juries for the American Academy in Rome. He was a long-time fellow of the American Society of Landscape Architects, and served as its national president from 1922 to 1927.