José Cassiano was born Giuseppe Cassini in San Remo, Italy, the son of Geronimo and Catalina Cassini. He arrived in New Orleans on November 20, 1816, with a British passport, as a resident of Gibraltar. In New Orleans he became a successful merchant and property owner. In connection with his business he made frequent trips to Texas and sometime in the 1820s moved to San Antonio, where he opened a store.
During the Siege of Béxar in December 1835 his home and store with its supplies were turned over to the revolutionary army. In 1835–36 he served as a scout along the Rio Grande. Just before the attack on the Alamo he sent messages to William B. Travis on the movements of Antonio López de Santa Anna. He made substantial contributions to finance the revolution. His aid to the cause of independence was recognized when Thomas J. Rusk, secretary of war, issued instructions on June 21, 1836, that Cassiano be permitted to travel freely between Texas and the United States.
Cassiano died on January 1, 1862, and is buried in San Fernando Cemetery in San Antonio.