Born in Qingdao, China, she was a daughter of Hugo Reiss (1879-), a Jewish, German-born diplomat who served as Brazil's consul in Shanghai, China. Her mother, a Roman Catholic, was Ignatia Mary Murphy (1891-), a native of San Francisco, California .
She had two sisters, Barry J. Reiss-Brian (died 1970, unmarried) and Huguette Reiss Gerard Hoguet (died 1994, married twice). By her mother's second marriage to Guy L. A. Brian, she had two half-sisters: Marie-Brigitte (1928-, Countess Bernard de La Rochefoucauld) and Patricia (1930-, Madame Jacques Bemberg).
All five daughters were raised as Catholics, with the three Reiss girls spending their infancy and early childhood in Shanghai, China. After Mary Reiss's marriage to Guy Brian, the family lived in Paris, and Jane graduated from the Convent des Oiseaux, a fashionable Catholic school in Neuilly, France; its alumni included the future Vietnamese empress Nam Phuong.
On 1 June 1939, she married Dr. Fritz Mannheimer (1890-1939), a German Jewish banker and art collector. The director of Mendelssohn & Co., Amsterdam, a branch of a fabled private bank headquartered in Berlin and known for floating multi-million-dollar loans to various European governments, including that of Germany, he died eight weeks after the wedding, reportedly of a heart attack, on 9 August 1939. The actual cause of Mannheimer's death remains as speculative as its timing was suspicious. One day after his death, the Amsterdam branch announced that it was insolvent and that it was confiscating Mannheimer's art collection, which had been financed with unlimited bank credit. Shortly thereafter, the entire firm was liquidated by the German government.
The couple had one child, Anne France Mannheimer (Annette de la Renta) (1939-), who was born after Mannheimer's death.
Jane Mannheimer moved first to London, then to New York City after her first husband's death. In 1947 she was named vice president of the merchandising division of Holbrook Microfilming Service, a company which was headed by president John J. Raskob and chairman Lt. Gen. Hugh Drum. She also was a member of Sillman & Associates, through which she was a minor investor in Broadway revues such as "New Shoes" and "Gentlemen Be Seated."
In 1947, she married Charles W. Engelhard, Jr. (1917-1971), a multimillionaire minerals industrialist from New Jersey. The couple lived in Far Hills, New Jersey, where they raised golden retrievers and thoroughbred race horses, including the fabled Triple Crown of Thoroughbred Racing champion, Nijinsky. They had numerous homes, including Cragwood, a 1920s neo-Georgian mansion in New Jersey, a country house in South Africa, and residences in London, Paris, Maine, Nantucket, New York City, and Quebec's Gaspé Peninsula.
The Engelhards had four daughters: Susan Engelhard, Jane Elizabeth Sophia Engelhard, Sally Alexandra Engelhard, and Charlene B. Engelhard. Charles Engelhard also adopted his wife's daughter from her first marriage.
Jane Engelhard was a patron of numerous causes and institutions, including the New Jersey Symphony. She served on the Boards the Metropolitan Museum of Art and the Morgan Library for many years. She also was a member of the Fine Arts Committee of the White House, organized during the Kennedy administration; the decoration of the Small State Dining Room is among her reported contributions to the restoration of the White House. In 1977, Engelhard was the first woman appointed as a Commissioner of the Port Authority of New York and New Jersey. She was also a member of the Library of Congress Trust Fund Board and a recipient of the Legion d'honneur.
She died in Nantucket, Massachusetts.