Silverheels excelled in athletics, most notably in lacrosse, before leaving home to travel around North America. In 1931, owners of NHL’s franchises in Toronto and Montreal created indoor lacrosse (also known as “box lacrosse”) as a means to fill empty arenas during the summer months, and, playing as Harry Smith, Silverheels was among the first players chosen to play for the Toronto Tecumsehs. Along with his brothers and cousins Russell (Beef), Sid (Porky) and George (Chubby), he also played on teams in Buffalo, Rochester, Atlantic City, and Akron throughout the 1930s on teams in the North American Amateur Lacrosse Association. He lived for a time in Buffalo, New York, and in 1938 placed second in the Middleweight class of the Golden Gloves tournament. Silverheels was inducted into the Canadian Lacrosse Hall of Fame as a veteran player in 1997.

While playing in Los Angeles on a touring box lacrosse team in 1937, Silverheels impressed Joe E. Brown, with his athleticism. Brown encouraged him to do a screen test, which led to his acting career. Silverheels began working in motion pictures as an extra and stunt man in 1937. He was billed variously as Harold Smith and Harry Smith, and appeared in low-budget features, westerns, and serials. He adopted his screen name from the nickname he had as a lacrosse player. Jay Silverheels was cast in a short feature film, I Am an American (1944). From the late 1940s, he played in major films, including Captain from Castile starring Tyrone Power (1947), Key Largo with Humphrey Bogart (1948), Lust for Gold with Glenn Ford (1949), Broken Arrow (1950) with James Stewart, War Arrow (1953) with Maureen O’Hara, Jeff Chandler and Noah Beery Jr., The Black Dakotas (1954) as Black Buffalo, Drums Across the River (1954), Walk the Proud Land (1956) with Audie Murphy and Anne Bancroft, Alias Jesse James (1959) with Bob Hope, and Indian Paint (1964) with Johnny Crawford. He made a brief appearance in True Grit (1969) as a condemned criminal about to be executed. He played a substantial role as John Crow in Santee (1973), starring Glenn Ford. One of his last roles was a wise white-haired chief in The Man Who Loved Cat Dancing (1973).

Married in 1945, Silverheels was the father of first son, Steve, four daughters named Marilyn, Gail, Pamela, and Karen, and a second son, Jay Anthony Silverheels Junior, who also was briefly an actor.

When The Lone Ranger television series ended, Silverheels continued to be typecast as a Native American. On January 6, 1960, he portrayed a Native American fireman trying to extinguish a forest fire in the episode “Leap of Life” in the syndicated series, Rescue 8, starring Jim Davis and Lang Jeffries.

Eventually, he went to work as a salesman to supplement his acting income. He also began to publish poetry inspired by his youth on the Six Nations Indian Reserve and recited his work on television. In 1966, he guest-starred as John Tallgrass in the short-lived ABC comedy/western series The Rounders, with Ron Hayes, Patrick Wayne, and Chill Wills.

Despite the typecasting, Silverheels in later years often poked fun at his character. In 1969, he appeared as Tonto without The Lone Ranger in a comedy sketch on The Tonight Show Starring Johnny Carson. The sketch was featured on the 1974 record album Here’s Johnny: Magic Moments from the Tonight Show. “My name is Tonto. I hail from Toronto and I speak Esperanto.” In 1970, he appeared in a commercial for Chevrolet as a Native American chief who rescues two lost hunters, who had ignored his advice, in that year’s Chevy Blazer. The William Tell Overture is heard in the background.

Silverheels suffered a stroke in 1976, and the following year, Clayton Moore – his co-star on The Lone Ranger – rode a paint horse in Silverheels’ honor in the Pasadena Tournament of Roses Parade. Silverheels died on March 5, 1980, from complications of a stroke, at age sixty-seven, in Calabasas, Los Angeles County, California. He was cremated at Chapel of the Pines Crematory, and his ashes were returned to the Six Nations Reserve in Ontario.

In 1993, Silverheels was inducted into the Hall of Great Western Performers at the National Cowboy & Western Heritage Museum in Oklahoma City, Oklahoma. He was named to the Western New York Entertainment Hall of Fame, and his portrait hangs in Buffalo, New York’s Shea’s Buffalo Theatre. He has a star on the Hollywood Walk of Fame at 6538 Hollywood Boulevard. First Americans in the Arts honored Silverheels with their Life Achievement Award.

In 1997, Silverheels was inducted, under the name Harry “Tonto” Smith, into the Canadian Lacrosse Hall of Fame in the Veteran Player category in recognition of his lacrosse career during the 1930s.