The yacht was purchased on 10 October 1956 for MX$50,000 (US$15,000) from the U.S.-based Schuylkill Products Company, Inc. by a Mexican citizen—said to be Mexico City gun dealer Antonio "The Friend" del Conde—secretly representing Fidel Castro. Castro's 26th of July Movement had attempted to purchase a Catalina flying boat or a US naval crash rescue boat for the purpose of crossing the Gulf of Mexico to Cuba, but their efforts had been thwarted by lack of funds. The money to purchase the Granma had been raised in the U.S. state of Florida by former President of Cuba Carlos Prío Socarrás.
Shortly after midnight on 25 November 1956 in the Mexican port of Tuxpan, Veracruz, the Granma was surreptitiously boarded by 82 members of the 26th of July movement including their leader, Fidel Castro, his brother, Raúl Castro, Che Guevara and Camilo Cienfuegos. The group—who later came to be known collectively as los expedicionarios del yate Granma—set out from Tuxpan at 1 a.m. and, after a series of vicissitudes and misadventures, including the near-foundering of their heavily overladen and leaking craft, disembarked on 2 December on the Playa Las Coloradas, Municipality of Niquero, in what is now Granma Province (after the vessel), but was then part of the larger Oriente Province. The Granma was piloted by Norberto Collado Abreu, a Cuban Navy veteran and ally of Castro. The location was chosen to emulate the voyage of national hero José Martí, who had landed in the same region 61 years earlier during the wars of independence from Spanish colonial rule.