On the 16th of November 1920, Anthony was born in Manhattan, New York, to Italian immigrant parents. His father was a tailor, his mother was a homemaker, and he grew up in Manhattan. When Anthony was 20, he enlisted in the US Marine Corps and he was assigned to the 5th Marines, 1st Marine Division after recruit training at Parris Island. Six months after the Japanese attacks on Pearl Harbor, Anthony was deployed with the 5th Marines to the south Pacific and took part in the landing on Guadalcanal in August of 1942. It was his actions three months later that would later earn him the Medal of Honor. The citation reads:

For conspicuous gallantry and intrepidity at the risk of his life above and beyond the call of duty while serving with Company D, First Battalion, Fifth Marines, First Marine Division on Guadalcanal, British Solomon Islands, in action against the enemy Japanese forces on 1 November 1942. Serving as a leader of a machine gun section, Cpl. Casamento directed his unit to advance along a ridge near the Matanikau River where they engaged the enemy. He positioned his section to provide covering fire for two flanking units and to provide direct support for the main force of his company which was behind him. During the course of this engagement, all members of his section were either killed or severely wounded and he himself suffered multiple, grievous wounds. Nonetheless, Cpl. Casamento continued to provide critical supporting fire for the attack and in defense of his position. Following the loss of all effective personnel, he set up, loaded, and manned his unit's machine gun, tenaciously holding the enemy forces at bay. Cpl. Casamento singlehandedly engaged and destroyed one machine gun emplacement to his front and took under fire the other emplacement on the flank. Despite the heat and ferocity of the engagement, he continued to man his weapon and repeatedly repulsed multiple assaults by the enemy forces, thereby protecting the flanks of the adjoining companies and holding his position until the arrival of his main attacking force. Cpl. Casamento's courageous fighting spirit, heroic conduct, and unwavering dedication to duty reflected great credit upon himself and were in keeping with the highest traditions of the Marine Corps and the U.S. Naval Service.

Anthony was evacuated and treated at a medical station and was then returned to the States, where he received more medical treatment in a naval hospital in Oakland, California. During his deployment, he had been wounded fourteen times, which left him permanently disabled. It was thought that all witnesses to his actions had died that day, so when he was recommended for the Medal of Honor, it was downgraded to the Navy Cross in 1965. Anthony refused to accept the Navy Cross and instead he stayed outside the White House for 51 days in his wheelchair. It was learned that two eyewitnesses of Anthony’s actions had survived and on the 12th of September 1980, his Navy Cross was upgraded to the Medal of Honor and he received it from President Carter at a ceremony at the White House. After a long fight with cancer, Anthony Casamento died on the 18th of July 1987, at the age of 66. He and his wife Olivia had four daughters: Mary, Jane, Ann, and Catherine. His Medal of Honor is on display at the West Islip Public Library in New York, along with a White House photo album, a watch from the Congressional Medal of Honor Society, and some personal memorabilia that was donated to the library by his daughter Mary. Anthony is buried in the Long Island National Cemetery in East Farmingdale, New York: Distinguished Service Section, Site 79A.