Giacomo Patri was born in Italy in 1898. As an infant he was stricken with polio causing him to use a cane throughout his life. In 1916, at the age of 18, he arrived in San Francisco and found work as a tailor, elevator operator, and in a mattress factory. In 1917 he helped found a literary and drama club in the basement of his parents' home. Despite his polio he took up fencing and in 1923 won third place in the Amateur Fencing League of America. He attended the California School of the Arts where he was mentored by Spencer Macky, Ralph Stackpole, Horatio Nelson Poole, and Gottardo Piazzoni. He landed an illustrators job in the San Francisco Examiner advertising department but soon left to return to school full time.

Graduating during the height of the Great Depression, he was unable to find a job but survived by providing instruction in drawing, fencing, and Italian, and by painting signs and murals for local stores. Through the National Recovery Act he found work at the Call Bulletin doing cartooning and photo retouching. He was a founding member of the local chapter of the Newspaper Guild and served as president of the Artist Guild. In 1937 he began working for theSan Francisco Chronicle as an illustrator and at the start of WWII was given a page of his own to graphically dramatize the war effort. While at the Chronicle he perfected his scratchboard technique, which became his chief vehicle of artistic expression. He also began teaching art to working men and women at the California Labor School where he developed his teaching philosophy that "creativity is present in everyone, that its expression is a basic human need..."

Beginning in 1937 and throughout the 1940s, Patri created illustrations for many labor union publications, including the Marine Cooks and Stewards Association, ILWU Warehouse Local 6, and the Pile Drivers, Bridge, Wharf and Dock Builders Local 34. In 1940, Patri published White Collar, a textless book featuring his linocut illustrations chronicling the plight of workers during the Great Depression. The book was reprinted in 1987 by his wife, Tamara Rey Patri. In 1948 Patri founded the Patri School of Art Fundamentals based on his teaching philosophy. The school closed in 1966 upon Patri's retirement.