Schoendienst was born in Germantown, Illinois, approximately 40 miles (64 km) east of downtown St. Louis to Joe and Mary Schoendienst, one of seven children. His father was a coal miner, and the family lived without running water or electricity.
Schoendienst showed a marked aptitude for baseball at a young age. In school he would handicap himself by hitting left-handed. In 1939, at age 16, he dropped out of school to join the Civilian Conservation Corps, a major, public works, employment program within President Franklin D. Roosevelt's New Deal. While working on a fence, he suffered a serious injury to his left eye from a nail. Many doctors recommended removal of the eye, but eventually Red found one willing to pursue non-surgical treatment. He endured constant headaches and years of rehabilitation.
After the eye injury, Schoendienst found it very difficult to read breaking balls while batting right-handed against right-handed pitchers. To solve the problem, he used the left-handed batting skills he acquired as a youth to become a switch hitter. In the spring of 1942, he participated in a St. Louis Cardinals open tryout with about 400 other hopefuls. Though he was not signed at the tryout, Joe Mathes, the Cardinals' chief scout, later changed his mind and drove to Germantown to sign him for $75 a month.
Schoendienst began his professional career in the D-level Georgia–Florida League with the Albany Cardinals, followed by the Union City Greyhounds of the Class D Kentucky–Illinois–Tennessee League. At Union City, he collected eight hits in his first eight at bats (AB) on his way to batting .407 in six games. In 1943, after playing nine games for the Lynchburg Cardinals in the Class B Piedmont League, he had attained 17 hits in 36 AB. This strong start earned him a promotion to the double-A International League's (IL) Rochester Red Wings, where he batted .337 in 136 games with 21 doubles, six home runs (HR) and 20 stolen bases (SB). His .337 average was the league's best; he was named the IL's Most Valuable Player (MVP) and gained visibility as a top prospect.
In 1944, still in Rochester, Schoendienst hit .373 in 25 games. He was drafted mid-season by the Army, but received a medical discharge on January 1, 1945, due to his eye injury and sustained trauma incurred while shooting bazookas.
The Cardinals invited Schoendienst for spring training in Cairo, Illinois, in 1945. Schoendiest had been a shortstop in the minor leagues and because Marty Marion, the incumbent shortstop, had been the National League MVP IN 1944 and was still considered the best shortstop in the league, St. Louis assigned Schoendienst to be the left fielder. Totaling 137 games in his rookie season, he batted .278 with a league-high 26 SB. In 1946, the Cardinals moved Schoendienst to play second base on their way to their third World Series title in five years. During the 1946 offseason, he won the televised home run derby. With sure hands and quick reflexes, he led the National League's second basemen for seven seasons and handled 320 consecutive chances without an error in 1950. In that season's All-Star Game, he won the contest for the National League with a home run in the top of 14th inning. It was the first All-Star game to go to extra innings. His 1956 league record fielding percentage of .9934 stood for 30 years until broken by Ryne Sandberg.
In 1956, the Cardinals traded him to the New York Giants, who dealt him the following season to the Milwaukee Braves, where he helped lead the team to its first pennant in nine years, batting .309 and finishing third in the NL MVP vote. In the World Series the Braves defeated the New York Yankees to win their only world championship in Milwaukee, and the franchise's first since 1914. Milwaukee repeated as NL champions in 1958 but lost to the Yankees in their World Series rematch; Schoendienst flied out to Mickey Mantle for the Series' final out.
During the 1958–59 off-season Schoendienst was diagnosed with tuberculosis and underwent a partial pneumonectomy in February 1959. Despite being told that he would never play again, he returned to the Braves in 1960—only to be released at the end of the season. In 1961 he rejoined the Cardinals, first as a pinch hitter, then as a coach when Johnny Keane replaced Solly Hemus as the Cardinals' manager. In his final two playing seasons he served as a player-coach, batting over .300 in both 1962 and 1963.
In 19 seasons as a player, Schoendienst compiled a .289 batting average with 84 home runs, 773 RBI, 1223 runs, 2449 hits, 427 doubles, 78 triples and 89 stolen bases in 2216 games played. His defensive statistics as a second baseman included 4616 putouts, 5243 assists, 1368 double plays, and only 170 errors in 10029 total chances for a .983 fielding average.
Keane resigned the day following the Cardinals' 1964 World Series victory over the Yankees, and Schoendienst was named as his replacement. Three years later, the Cardinals defeated the Boston Red Sox—Schoendienst's fourth World Series title, and third as a Cardinal. His managerial record over 12 full seasons (1965–76) and two subsequent stints as interim manager (1980 and 1990) was 1,041 victories and 955 defeats (.522). After two years as a coach for the 1977–78 Oakland Athletics, Schoendienst returned to the Cardinals as coach and special assistant to the general manager. He won his fifth Series title in 1982. He remains an employee of the Cardinals organization with the title of Special Assistant Coach, and in 2016 completed his 71st consecutive season as a Major League player, coach, or manager.
Schoendienst was a member of five winning World Series teams, all of which won in seven games: as a player with the Cardinals and Braves in 1946 and 1957 respectively; as the Cardinals manager in 1967; and as a Cardinals coach in 1964 and 1982. He was also a member of three teams that lost the Series after leading three games to one: the 1958 Milwaukee Braves (to the Yankees), the 1968 Cardinals (to the Detroit Tigers), and the 1985 Cardinals (to the Kansas City Royals).
Schoendienst was elected to the Baseball Hall of Fame in 1989 by the Veterans Committee. The Cardinals retired his number 2 in 1996. In 1998 he was inducted into the St. Louis Walk of Fame. The Cardinals named Schoendienst, among 21 other former players and personnel, to be inducted into the St. Louis Cardinals Hall of Fame Museum for the inaugural class of 2014.
In 1947, Schoendienst married the former Mary Eileen O'Reilly, who died in 1999. Their 52-year marriage produced three daughters (Colleen, Cathleen, and Eileen) and one son (Kevin). As of 2016, Schoendienst lives in Town and Country, Missouri – a western suburb of St. Louis.
Schoendienst is the last living member of the Cardinals team that won the 1946 World Series. There are no living players who played on an earlier World Series-winning team.