Carlton has the second-most lifetime strikeouts of any left-handed pitcher (4th overall), and the second-most lifetime wins of any left-handed pitcher (11th overall). He was the first pitcher to win four Cy Young Awards in a career. He held the lifetime strikeout record several times between 1982 and 1984, before his contemporary Nolan Ryan passed him. One of his most remarkable records was accounting for nearly half (46%) of his team's wins, when he won 27 games for the last-place (59-97) 1972 Phillies. He is the last National League pitcher to win 25 or more games in one season, as well as the last pitcher from any team to throw more than 300 innings in a season. He also holds the record with the most career balks of any pitcher, with 90 (double the second on the all-time list, Bob Welch).
Carlton debuted with the St. Louis Cardinals as a 20-year-old in 1965 and by 1967 was a regular in the Cardinals rotation. An imposing 6 feet 4 inches (1.93 m) man with a hard fastball and slider, Carlton was soon known as an intimidating and dominant pitcher. Carlton enjoyed immediate success in St. Louis, posting winning records and reaching the World Series in 1967 and 1968. On September 15, 1969, Carlton struck out 19 New York Mets, while losing to the Mets, 4–3, setting the all-time modern-day record at that time for strikeouts in a nine-inning game. That season, he finished with a 17–11 record with a 2.17 ERA, second lowest in the NL, and 210 strikeouts. A contract dispute with the Cardinals (he had made $26,000 in 1969 and was holding out for $50,000, as opposed to the Cardinal's contract offer for just $31,000)[nb 1]made Carlton a no-show at spring training in 1970. He proceeded to go 10–19 with a 3.73 ERA, leading the NL in losses. In 1971, he became a 20-game winner for the first time, going 20–9 with a 3.56 ERA.
The trade is now considered one of the most lopsided deals in baseball history. However, at the time, the trade appeared to make some sense from the Cardinals' perspective. Carlton had won 77 games to Wise's 75, and both were considered among the best pitchers in the game. Tim McCarver, who had caught for Carlton in St. Louis and for Wise in Philadelphia, described the trade as "a real good one for a real good one." He felt that Carlton had more raw talent, but Wise had better command on the mound. Although Wise would stay in the majors for another 11 years (though only two of them were with the Cardinals), the trade is now reckoned as an epoch-making deal for the Phillies, as well as one of the worst trades in Cardinals history.
In Carlton's first season with Philadelphia, he led the league in wins (27), complete games (30), strikeouts (310), and ERA (1.97), despite playing for a team whose final record was 59–97. His 1972 performance earned him his first Cy Young award and the Hickok Belt as the top professional athlete of the year. His having won 46% of his team's victories that season is a record in modern major league history. Carlton attributed his success to his grueling training regimen, which included Eastern martial arts techniques, the most famous of which was twisting his fist to the bottom of a 5 gallon bucket of rice.
Some highlights of Carlton's 1972 season included starting the season with 5 wins and 1 loss, then losing 5 games in a row, during which period the Phillies scored only 10 runs. At this point he began a 15-game winning streak. After it ended at a 20–6 record, he finished the final third of the year with 7 more wins and 4 losses, ending with 27 wins and 10 losses. Carlton also completed 30 of 41 starts..
During the 18 games of the winning streak (3 were no-decisions), Carlton pitched 155 innings, allowed 103 hits and 28 runs (only 17 in the 15 winning games), issued 39 walks, and had 140 strikeouts. From July 23, 1972 to August 13, 1972 he pitched five complete game victories, allowed only 1 unearned run while only giving up 22 hits in 45 innings, and threw four shutouts. He had a fastball, a legendary slider, and a long looping curve ball; and later a change-up, then a screwball. Baseball commentators during 1972 regularly remarked that Carlton's slider was basically unhittable. He was also a good hitter for a pitcher; at times he pinch-hit for the Phillies during 1972.
Carlton slumped in 1973, losing 20 games. The media's open questioning of his unusual training techniques led to an acrimonious relationship between them and Carlton, and he severed all ties with the media, refusing to answer press questions for the rest of his career with the Phillies. This reached a point where, in 1981, while the Mexican rookie Fernando Valenzuela was achieving stardom with the Los Angeles Dodgers, a reporter remarked, "The two best pitchers in the National League don't speak English: Fernando Valenzuela and Steve Carlton."
In 1994 he agreed to an interview with writer Pat Jordan his home in Durango, Colorado. The result was the story "Thin Mountain Air" in the April 1994 issue of Philadelphia magazine. 
Carlton continued to enjoy many years of success with the Phillies, winning the Cy Young Award in 1972, 1977, 1980, and 1982, and pitching the Phillies to the best string of post-season appearances in club history. Carlton was the first pitcher to win four Cy Young Awards, a mark later matched by Greg Maddux, and exceeded by Roger Clemens and Randy Johnson. His Cy Young Award in 1972 was by unanimous vote, and he finished fifth in balloting for the National League MVP. Gradually the Phillies improved their team, and won the National League East three consecutive times from 1976 to 1978. In 1980, Carlton helped the Phillies win their first World Series, personally winning the final game.
On September 13, 1982, for the fourth time in his career, Steve Carlton hit a home run and tossed a complete game shutout in the same game. He is the only pitcher to have done so in three different decades.
On September 23, 1983, in a game against the St. Louis Cardinals, Carlton won the 300th game of his career, becoming the 15th pitcher to accomplish the feat.
Race with Nolan Ryan and Gaylord Perry for the all-time strikeout record
Over a three-year period between 1982–1984, Carlton was involved in an interesting pitching duel with Nolan Ryan and Gaylord Perry, in which they often traded places at the top of the all-time strikeout list.
At the start of the 1982 season, the 55-year-old mark of the great Walter Johnson still stood at 3,508 strikeouts, but now there were three pitchers who would start the season within 100 strikeouts of Johnson: Nolan Ryan (3,494), Gaylord Perry (3,452), and Carlton (3,434). Ryan would be the first to surpass Johnson on April 22, 1983 against the Montreal Expos. However a stint on the disabled list shortly after he set the record, combined with a spectacular season by Carlton, allowed Carlton to make up ground and on June 7, 1983, Carlton passed Ryan as the all-time strikeout king with 3,526 to Ryan's 3,524. There would be a total of 14 lead changes and one tie that season, often after each of their respective starts, before the season ended with Carlton leading 3,709 to 3,677. Gaylord Perry, aging and in his final season, was never a huge factor, although he did eventually pass Johnson to finish his career with 3,534 strikeouts. Since then five other pitchers have surpassed Johnson's mark and he has fallen to ninth place on the all-time strikeout list.
There would be five more lead changes and a tie in 1984 before Carlton ran out of gas. His last-ever lead in the all-time strikeout race was after his start on September 4, 1984, when he struck out four Cubs to lead Ryan by three (3,857 to 3,854). Although the season ended with a mere two-strikeout lead for Ryan (3,874 to 3,872), Carlton had an injury-riddled season in 1985 and an even worse season in 1986 before being released by the Phillies just 18 strikeouts short of 4,000.
He joined the San Francisco Giants, but pitched ineffectively for seven shutout innings in a game against the Pittsburgh Pirates, in which he also hit a 3-run homer, for his only win as a Giant. He would hang around just long enough to collect his 4,000th strikeout (against Eric Davis) before retiring. He went 1–3 with a 5.10 ERA in six games for the Giants. He did, however, break his self-imposed boycott of the media, giving a press conference after signing with the Giants.
His retirement was brief: he almost immediately signed with the Chicago White Sox for the remainder of the 1986 season. He was surprisingly effective, going 4–3 with a respectable 3.69 ERA, but was not offered a contract for 1987.
He joined the Cleveland Indians, where his most notable achievement was teaming up with Phil Niekro in a game against the New York Yankees at Yankee Stadium, where they became the first teammates and 300-game winners to appear in the same game. Both were ineffective in a 10–6 Yankee victory. It would be his first and only pitching appearance in Yankee Stadium, having spent the majority of his career in the National League before the inception of interleague play. (He was selected to the 1977 National League All-Star team which was held in Yankee Stadium, but he didn't appear in the game.)
He was traded to the Minnesota Twins, where he was yet again ineffective. He went a combined 6–14 with a 5.74 ERA for both the Indians and Twins. However, the Twins, who had been a bad team for most of the 1980s, would go on to a surprising win in the 1987 World Series, albeit without Carlton on the postseason roster, to earn him a third World Series ring and a trip to the White House to meet PresidentReagan along with his teammates. Interestingly, when Carlton was photographed with his teammates at the White House, newspapers listed each member of the team with the notable exception of Carlton. Instead, Carlton was listed as an "unidentified Secret Service agent." The Twins brought him back in 1988 but he lasted only a month (0-1 with a 16.76 ERA in four games) before the Twins released him.
He attempted to find work in 1989 but found no takers. The closest thing to an offer was the New York Yankees offering him the use of their facilities for training purposes but no spot on the spring training team. Nolan Ryan would pitch until 1993 and would extend his strikeout lead over Carlton to almost 1,600 before retiring. Carlton would eventually fall to third and then fourth place on the all-time strikeout list after Roger Clemens and Randy Johnson passed him.
Carlton picked 144 runners off base, by far the most in Major League Baseball since pickoff records began being collected in 1957. Jerry Koosman is second with 82.
He never threw a no hitter, but pitched six one-hitters.
Carlton was elected to the Baseball Hall of Fame in 1994 with 96% of the vote, one of the highest percentages ever. The Phillies retired his number 32 in 1989, and honored him with a statue outside Citizens Bank Park in 2004.
Despite his career-long rivalry with Ryan, Carlton maintains his greatest rival was Tom Seaver.
His losing 19-strikeout effort against the Mets was a microcosm of his career against them. While he posted 30 wins against them during his career, they bested him 36 times.
Carlton appeared in an episode of Married... with Children, playing himself in an episode where former athletes humiliate Al Bundy while filming a shoe commercial. In the episode, Bud asks him for an autograph and he is shown writing with his right hand.