Smith grew up in Los Angeles, CA and attended Centennial High School (Compton, California). He won the International League batting title in 1966 with a .320 average while playing for the Toronto Maple Leafs. He was called up to the MLB late in that season and played for the Boston Red Sox (1966–73), St. Louis Cardinals (1974–76), Los Angeles Dodgers (1976–81) and San Francisco Giants (1982). Smith appeared in four World Series, including during his rookie 1967 season for the Red Sox, and three (1977, 1978 and 1981) for the Dodgers. He hit three home runs in the 1977 series.

In the 1978 season, Dodger pitcher Don Sutton went public with comments that Smith was a more valuable player to the Dodgers than the more-celebrated Steve Garvey. This led to an infamous clubhouse wrestling match between Sutton and Garvey.

In the 1981 season as a member of the Dodgers, Smith was taunted by Giants fan Michael Dooley, who then threw a batting helmet at him. Smith then jumped into the stands at Candlestick Park and started punching him. He was ejected from the game, and Dooley was arrested. Five months later, Smith joined the Giants as a free agent. He spent one season in San Francisco, then moved on to NPB with the Yomiuri Giants for two seasons before retiring in 1984.

In 1,987 games over 17 seasons, Smith posted a .287 batting average (2020-for-7033) with 2,020 hits, 1,123 runs, 363 doubles, 57 triples, 314 home runs, 1,092 RBI, 137 stolen bases, 890 base on balls, 1,030 strikeouts, a .366 on-base percentage, and a .489 slugging percentage. He recorded a career .978 fielding percentage. In four World Series and four playoff series covering 32 games, he hit .234 (25-for-107) with 17 runs, 6 home runs, and 17 RBI.

Smith became involved with USA Baseball in 1999 as hitting coach on the 1999 Professional Team at the Pan American Games in Winnipeg, Canada (Silver, Olympic qualifiers). Smith again served as USA hitting coach in the 2000 Olympic Games in Sydney, Australia where the US Team took home Gold. He also served as hitting coach for the 2007IBAF Baseball World Cup in Taiwan (Gold). Smith also served as hitting coach for Team USA during the 2006 World Baseball Classic, and served as hitting coach for the Bronze medal winning USA Baseball Olympic team at the 2008 Summer Olympics in Beijing.