One of the famous "Whiz Kids" of the National League champion 1950 Phillies, Ashburn spent 12 of his 15 major-league seasons as the Phillies' center fielder (1948–1959). He sported a .308 lifetime batting average, leading the National League twice, and routinely led the league in fielding percentage. In 1950, in the last game of the regular season, he threw Dodgers' runner Cal Abrams out at home plate to preserve a 1–1 tie and set the stage for Dick Sisler's pennant-clinching home run. He had been playing in to back up a pick-off throw on a pitchout, but pitcher Robin Roberts had instead thrown a fastball to the batter, Duke Snider.^[1]

The following year Ashburn displayed his fielding skill on the national stage in the All-Star Game at Tiger Stadium in Detroit. The Associated Press reported, "Richie Ashburn, fleet footed Philadelphia Phillies outfielder, brought the huge Briggs Stadium crowd of 52,075 to its feet with a brilliant leaping catch in the sixth inning to rob Vic Wertz of a near homer. Ashburn caught the ball in front of the right centerfield screen 400 feet distant after a long run."^[2] He was also the last Phillies player to collect eight hits in a double-header when he singled eight times in a twinbill at Pittsburgh on May 20, 1951.

Ashburn was a singles hitter rather than a slugger, accumulating over 2,500 hits in 15 years against only 29 home runs. In his day he was regarded as the archetypal "spray hitter", stroking the ball equally well to all fields, thus making him harder to defend against. Ashburn accumulated the most hits (1,875) of any batter during the 1950s.^[3]

During a game on August 17, 1957, Ashburn hit a foul ball into the stands that struck spectator Alice Roth, wife of Philadelphia Bulletin sports editor Earl Roth, breaking her nose. When play resumed Ashburn fouled off another ball that struck her while she was being carried off in a stretcher.^[4] Ashburn and Roth maintained a friendship for many years, and the Roths' son later served as a Phillies batboy.

Ashburn was purchased by the expansion New York Mets for the 1962 season and was the first batter in franchise history. He had a good year offensively, batting .306, and was the team's first All-Star Game representative. It was, however, a frustrating year for the polished professional, who had begun his career with a winner and found himself playing for the least successful team in modern baseball history (with a record of 40–120). He retired at the end of the season.Ashburn was traded to the Chicago Cubs following the 1959 season for three players. He went on to anchor center field for the North Siders in 1960 and 1961. Anticipating a future career behind a microphone, Ashburn sometimes conducted a post-game baseball instruction clinic at Wrigley Field for the benefit of the youngsters in the WGN-TV viewing audience.

One oft-told story is that on short flies to center or left-center, center fielder Ashburn would collide with shortstop Elio Chacón. Chacón, from Venezuela, spoke little English and had difficulty understanding when Ashburn was calling him off the ball. To remedy matters teammate Joe Christopher taught Ashburn to say "Yo la tengo", Spanish for "I’ve got it." When Ashburn first used this phrase it worked fine, keeping Chacón from running into him. But then left fielder Frank Thomas, who did not speak a word of Spanish, slammed into Ashburn. After getting up Thomas asked Ashburn, "What the heck is a Yellow Tango?" This anecdote inspired the name of the American indie rock group Yo La Tengo.

In his last five seasons, Ashburn played for the 8th-place Phillies, the 7th-place Cubs, and the 10th-place Mets. The infamous first-year Mets club won only a quarter of its games, and Ashburn decided to retire from active play. The last straw might have been during the Mets' 120th loss, when Ashburn was one of the three Mets victims in a triple play pulled off by his former teammates, the 9th-place Cubs. According to Jimmy Breslin, it was the prospect of sitting on the bench that led Ashburn to retire: "He sat on the bench for a while with another team once and it bothered him badly. And he said that if he ever had to be a benchwarmer for the New York Mets he'd commit suicide."^[5]

Throughout his playing career, Ashburn, who lived in his hometown of Tilden during the offseason, officiated high school basketball games throughout Nebraska as a way to stay in playing condition. He became a well-respected official, but retired from officiating when he retired from baseball.