Smith was born in Toronto in 1925. He played minor hockey in the Toronto league and joined the Oshawa Generals in the Ontario Hockey League as a 19-year-old. The next season he played with three teams in three leagues, including the National Hockey League with his hometown Maple Leafs for 14 games.
He spent half of the next season with the Leafs, but almost had his career ended during a game in March of 1948 after injuring his knee. Smith was placed in the Pittsburgh Hornets' lineup in 1948-49 to rehabilitate the knee and work on his game. The off-season conditioning paid off as he led the American Hockey League in scoring with 112 points in 68 games. His total of 55 goals, matched that year by Carl Liscombe, stayed on the record books in the AHL for 34 years.
At the end of his year with the Hornets, he was promoted to the Leafs to bolster the team as it attempted to hoist the Stanley Cup for the third consecutive season. Smith had an immediate impact, scoring two goals and assisting on another in the first game of the semifinal series against the Boston Bruins. In the second game of the Stanley Cup finals against Gordie Howe and the Detroit Red Wings, Smith scored all three goals, each of them on the power-play, in a 3-1 Toronto win. At the end of the game, Howe asked reporters, "Who's Sid Smith?"
Toronto swept the Red Wings and won the record-setting third consecutive Cup, winning its ninth consecutive game in the final series. Smith had a regular spot with the Leafs the next season, playing on a line alongside Toronto captain Ted Kennedy and Bill Ezinicki, the trio that had been so productive in the playoffs.
Some of Smith's many goals were momentous, including an overtime goal in the 1951 Stanley Cup finals against Montreal, a series that featured extra-time thrillers in each of the five games it took for Toronto to win its fifth Cup in six years. He also scored the winning goal in the first televised Maple Leafs game, against the Boston Bruins on November 1, 1952.
A model of consistency, Smith recorded six consecutive seasons with 20 or more goals, achieving that distinction in 1954-55 along with Gordie Howe. Only four others had been so reliable?Cy Denneny, Brian Hextall, Maurice Richard and Ted Lindsay?and Smith led the Leafs in scoring categories for eight seasons, four times for goals and four times for total points. Twice Smith was awarded the Lady Byng Trophy as the league's most gentlemanly player, in 1951, when he cracked the top 10 in league scoring with 51 points, and again in 1955, when he recorded a career-high 33 goals. Three times he was a league All-Star, earning First Team honors in 1955. He played in the All-Star Game in seven of his eight full seasons in the NHL. When Teeder Kennedy retired at the beginning of the 1955-56 season, Smith was elected the team captain, a role he filled with his quiet brand of leadership for one season before Kennedy returned to put the "C" back on his sweater in late 1956.
Twelve games into the 1957-58 season, Smith decided to retire from the Maple Leafs. At the time of his retirement, only three active players?Howe, Richard and Lindsay?had scored more goals. He was the Leafs' top goal scorer of the decade and was involved in 25% of the team's scoring plays during his highly productive stay.
After retiring, Smith became a player-coach with the Whitby Dunlops, a senior team in the Ontario Hockey Association, in 1957.
On April 29, 2004 Sid Smith passed away.