The roots of the Nahmad family are in Aleppo, Syria, where Syrian Jewish banker Hillel Nahmad lived until just after the Second World War. Following anti-Jewish violence in 1947, Hillel Nahmad moved to Beirut, Lebanon and when the situation there became difficult, Hillel took his three sons, Joseph (Giuseppe), Ezra and David, to Milan in the early 1960s.

As teenagers in the 1960s, they began to deal in art. Ezra and David skip school to trade on the Italian stock market. At a Juan Gris exhibition in Rome organised by cubist dealer Daniel-Henry Kahnweiler, Ezra and David bought two works – the only pieces sold. Kahnweiler befriended them, selling them works by Picasso, Braque, Gris. With the emergence of the Red Brigades terror group in the 1970s, Milan was perceived as too dangerous, and the family moved again. Joseph and Ezra headed for Monaco, and David to New York City.

David Nahmad is also the 1996 Backgammon World Champion, and is known for betting large amounts of money on the game.

In 2011, Philippe Maestracci filed suit in the United States District Court for the Southern District of New York, seeking title to the 1918 Modigliani painting Seated Man with a Cane, valued at more than $25 million. Maestracci claimed that the painting had been looted from his grandfather, Oscar Stettiner, during World War II. In 2012, after Defendants moved to dismiss, Maestracci’s counsel withdrew that complaint. In 2015, the Limited Ancillary Administrator for the Estate of Oscar Stettiner filed suit in the Supreme Court of the State of New York, County of New York, seeking the same relief sought in federal court. The amended complaint in that action is currently the subject of a motion to dismiss with Defendants’ counsel arguing, among other things, that Defendants purchased the painting in good faith at a public Christie’s auction in London, that Oscar Stettiner did not actually own the subject painting, and that the case is being bankrolled by Business people who specialize in funding restitution claims in exchange for obtaining a percentage of any recovery or settlement. Plaintiff's counsel contends that this painting had been sold out of the possessions of Jewish art dealer Oscar Stettiner by an administrator appointed under the Nazi occupation of Paris. In a letter filed in court on May 25, 2016, Eve Livengood claimed the painting was purchased by her husband's grandfather in 1944 and was in the possession of the family for over 50 years, until the Christie's Auction. Defendants' counsel has vigorously questioned the accuracy and authenticity of Ms. Livengood's letter.

Helly Nahmad Gallery, on Madison Avenue, is a company run by David’s son Hillel "Helly" Nahmad, who took over his father’s earlier Davlyn Gallery in 2000.