Solow is married to Sculptor and jewelry designer Mia Fonssagrives, the daughter of Lisa Fonssagrives, a Swedish model and the French Photographer, Fernand Fonssagrives. They have two children and live in New York City. His son, Stefan Soloviev, works in the family real estate Business and runs an agriculture conglomerate called Crossroads Agriculture based in Colorado and New Mexico. He is ranked the 54th largest landowner in the United States.

In the 1970s, Solow obtained financing, and after buying out each of the many townhouses in that spot before, in collaboration with Architect Gordon Bunshaft, Solow built a 50-story office building at 9 West 57th Street. As of 2017, the building is still considered a desirable location because of its views of Central Park.

Solow is an extensive collector of modernist and renaissance art. Solow owns “Young Man Holding a Medallion” by Botticelli as well as paintings by Balthus, Henri Matisse, and Franz Kline; and sculptures by Alberto Giacometti. In February 2012, he sold a Francis Bacon painting for $33.5 million, a Joan Miro painting for $26.6 million, a Henry Moore sculpture for $30.1 million; and in February 2013, he sold an Amedeo Modigliani painting for $42.1 million. In May 2015 Solow sold Giacometti' s 1947 sculpture L'homme au doigt for $126.1 million, setting a world record for the most expensive sculpture ever sold.