Stallone made his acting debut alongside his Father in Rocky V (1990), the fifth installment of the Rocky franchise, playing Robert Balboa Jr., the onscreen son of his father's title character. He did not, however, reprise the same role in Rocky Balboa, the sixth installment of the Rocky films as he was working on his own film Vic. He also appeared with his dad in Daylight (1996). After that, he acted in lesser profile films.
Stallone attended Montclair College Preparatory School in Van Nuys, California, where he graduated in 1993. He later studied filmmaking at North Carolina School of the Arts for one year.
From 1994–1995, he attended the University of North Carolina School of the Arts to study Filmmaking.
In 1996, Stallone and film Editor Bob Murawski co-founded Grindhouse Releasing, a Los Angeles-based company dedicated to the restoration and preservation of exploitation films and B-movies. Stallone directed his first short film (outside of film school) Vic, which won the 2006 Boston Film Festival "Best New Filmmaker" award.
His last projects were appearances in Vincent Gallo's last two films, Promises Written in Water and The Agent. Both films were shown in main competition at the 2010 Venice Film Festival and in the Toronto International Film Festival. A photograph of Stallone as a young child beside his Father appears in the 2015 Creed, where it is stated that his character, Robert Balboa Jr., has since moved away to Vancouver.
Stallone was found dead on July 13, 2012 at his home in Studio City, Los Angeles. According to reports, he had not been heard from for four days prior to his death and died between three and seven days prior to being found. Empty prescription drug bottles were found at the scene, but after an autopsy and toxicology tests, the Los Angeles coroner determined that Sage died of heart attack caused by atherosclerosis, with no drugs detected other than an over the counter pain remedy. Stallone was a heavy smoker. At the time of his death, Stallone was reportedly engaged. Stallone's funeral was held on July 21 at St. Martin of Tours Catholic Church in Los Angeles. He is interred at Westwood Village Memorial Park Cemetery.