Mickey Vernon was born in Marcus Hook, Pennsylvania, and attended Villanova University, before making his major league debut on July 8, 1939. He was the father of Gay Vernon.

During World War II, he served in the United States Navy, missing the 1944 and 1945 seasons. He served with major league players Larry Doby and Billy Goodman on Ulithi in the South Pacific in 1945; both Goodman and Vernon personally inspired Doby to become a major league baseball player; Doby became the first African-American to break the baseball color line in the American League in 1947 with the Cleveland Indians.

Vernon played for 14 full major league seasons (400 at bats or more) in his 20-year career. He wound up batting over .335 twice, over .300 five times, and over .290 nine times. He was a two-time American League batting champion. In 1946, his .353 batting mark eclipsed Ted Williams’ .342 by 11 points. Then, in 1953, Vernon’s .337 average denied Cleveland’s Al Rosen (.336) the Triple Crown by just one one-thousandth of a point. The following year, 1954, Vernon had a career high 20 home runs, 97 RBIs, and a career high 14 triples. He led the AL in doubles with a total of 33. He also had 294 total bases, which was second in the AL, behind Minnie Miñoso.

Vernon posted a career .286 batting average with 172 home runs and 1,311 RBIs in 2,409 games. The left-hander averaged 88 RBIs a year, and had 11 seasons with 80 or more, 3 with 90 or more. He scored 1,196 runs with 137 stolen bases and a .359 on-base percentage. His career slugging percentage was .428, with a career high of .518 in 1953. He compiled 2,495 hits, with 490 doubles and 120 triples, in 8,731 at bats. He had 3,741 career total bases, with his career high coming in 1953 (315).

Over time, Vernon became one of the best-liked ballplayers, mainly through his unique personality and charismatic, but quiet, style. On September 1, 1960, after a season spent as the Pittsburgh Pirates’ first-base coach, Vernon was placed on the active list when MLB rosters expanded to 40 men. He appeared in nine regular-season games as a pinch hitter for Pittsburgh, notching an RBI single and an intentional walk in his nine plate appearances to become one of only 29 players in baseball history to have appeared in a major league game in four decades. By his final game played, on September 27, 1960, he was, at 42, the oldest player in the National League by almost a year, and one of the most popular figures in the game. He appeared in 2,409 MLB games without playing in the postseason, third most in history behind Ernie Banks and Luke Appling. Notably, on September 25, 1960, during Vernon’s time on the active list, the Pirates clinched the NL pennant; but he was not on the Pirate playing roster for the 1960 World Series, resuming his full-time coaching duties. He earned a World Series ring when the Bucs triumphed in seven games over the New York Yankees.

The following year, in 1961, he returned to Washington when he was named manager of the expansion Senators in their first year of existence. Inheriting the name and home field of the 1901–60 Washington franchise, now the Minnesota Twins, the expansion Senators were hastily constructed with an undercapitalized ownership, an MLB roster of castoff players, and an almost-nonexistent farm system. In Vernon’s two full seasons at the helm, 1961 and 1962, the Senators lost a combined 201 games. They were 14–26 and last in the ten-team American League when Vernon was fired on May 21, 1963. He finished with a career record of 135–227, a .373 winning percentage.

Vernon died from a stroke at age 90, on September 24, 2008. He had resided in Media, Pennsylvania.

In August 2008, he was named as one of the ten former players who began their careers before 1943 to be considered by the Veterans Committee for induction into the National Baseball Hall of Fame in 2009.