WASHINGTON — Joe Garagiola, who transformed a mediocre baseball playing career into almost six decades as a popular and joyously self-deprec-ating broadcaster, becoming the sport’s ambassador to the public and a host of the ‘‘Today’’ show, died Wednesday in Scottsdale, Ariz. He was 90.

He had been in ill health since a stroke and heart attack in 2013.

From 1946 to 1954, Mr. Garagiola was a catcher for the St. Louis Cardinals, Pittsburgh Pirates, Chicago Cubs, and New York Giants. Statistically, his career was eminently forgettable. He retired with a lifetime batting average of .257, hit 42 home runs, and knocked in 255 runs.

Instead, he left his mark on the airways. His folksy, engaging, and well-informed style behind the microphone made Mr. Garagiola one of the country’s favorite baseball broadcasters from the 1960s to the 1980s.

He followed onetime Cardinals pitcher Dizzy Dean into the announcer’s booth, the vanguard of a corps of professional athletes who became broadcasters once their playing days were over. He was the media father of the likes of baseball’s Tim McCarver and Bob Uecker, football’s Terry Bradshaw and Lynn Swann, and tennis’s John McEnroe and Chris Evert.

Although he did not reach the National Baseball Hall of Fame as a player, Mr. Garagiola was enshrined as a broadcaster in 1991, when he received the Hall of Fame’s Ford C. Frick Award. He was the first former player to receive the honor.

‘‘At the apex of his career, the acclaim Garagiola received was dreamlike,’’ William Taaffe wrote in Sports Illustrated in 1988. ‘‘No announcer, including John Madden in the ‘80s, was ever more popular.’’

Mr. Garagiola’s career stretched beyond baseball and included two stints as a co-host of NBC’s ‘‘Today’’ show — from 1967 to 1973 and again from 1990 to 1992 — and later nine years as anchor of the annual Westminster Kennel Club Dog Show from New York’s Madison Square Garden. He was also the host of TV game shows and wrote best-selling books about his improbably successful life.

His Italian immigrant parents sometimes questioned his career choice, wondering why he would devote his life to playing a game. In 1960, he appeared onstage at a campaign event for Democratic presidential candidate John F. Kennedy, flanked by former president Harry S. Truman and other politicos. Mr. Garagiola put his arm around Truman, knowing that his father would be watching on television.

‘‘Hey, Pop,’’ he said, looking into the camera, ‘‘I just want you to see who I’m hanging around with.’’

Before he retired from baseball in 1954, Mr. Garagiola was acquiring a reputation as a popular after-dinner speaker in his native St. Louis, with an endearing quality of self-mockery.

‘‘When I was coming up,’’ he reportedly said, ‘‘a scout reported that my speed was deceptive. He said I was slower than I looked.’’

The Cardinals hired Mr. Garagiola as a color commentator for the 1955 season, launching him on a career that would extend well into the 21st century. Along the way, he was a play-by-play announcer and color analyst for NBC’s ‘‘Game of the Week’’ for two decades. He appeared on World Series broadcasts off and on from 1961 to 1988.

Early in his career, he teamed with Hall of Fame announcer Harry Caray in St. Louis, and he replaced another Hall of Famer, Mel Allen, on New York Yankees telecasts in the 1960s. He went on to work alongside such renowned broadcasters as Lindsey Nelson, Bob Wolff, Curt Gowdy, Vin Scully, Dick Enberg, and Tony Kubek.

‘‘He’d bring new words to the booth,’’ Wolff told author Curt Smith for his 1987 book ‘‘Voices of the Game,’’ about broadcasters. ‘‘Instead of saying, ‘A runner almost slid into the shortstop,’ Joe’d say, ‘He almost stapled him to the bag.’’’

Without losing his affable, middle-American presence, Mr. Garagiola was a frequent guest and occasional guest host on ‘‘The Tonight Show.’’ As host of “Today’’ and “Tonight,’’ he interviewed members of the Beatles, Secretary of State Henry Kissinger, evangelist Billy Graham, Vice President Hubert H. Humphrey and Earth-orbiting astronauts.

Mr. Garagiola was the emcee of the game shows ‘‘He Said, She Said,’’ ‘‘Sale of the Century,’’ and ‘‘To Tell the Truth.’’ One of his best-known non-baseball broadcasting ventures came from 1994 to 2002 as host of the Westminster Kennel Club Dog Show.

Mr. Garagiola’s ‘‘ ‘what the heck is going on here’ approach,’’ television critic Lisa de Moraes wrote in the Washington Post in 2003, ‘‘came to personify the canine competition.’’ He was spoofed by actor Fred Willard in the 2000 Christopher Guest mock-documentary ‘‘Best in Show.’’

‘‘It always tickles me,’’ Mr. Garagiola told The Post. ‘‘I say to some people: ‘I played in the World Series, and I broadcast the World Series. I broadcast the All-Star Game. I’ve done the Today Show, the Tonight Show, the Tomorrow Show, the Yesterday Show, and the Day After Tomorrow Show.’ And people come up to me and say, ‘I love you in Westminster.’ ‘‘

The son of Italian immigrants, Joseph Henry Garagiola was born in St. Louis. His father was a brickyard worker.

The family lived in an Italian-American neighborhood known as the Hill. One of his neighbors and childhood playmates was Lawrence Peter Berra, who became better known as the Hall of Fame New York Yankee catcher Yogi Berra.

‘‘Not only was I not the best catcher in the major leagues, I wasn’t even the best catcher on my street,’’ Mr. Garagiola said.

He played for Cardinals farm teams before being drafted into the Army in World War II. He was bound for the Pacific when the war ended.

Back home in 1946, he joined the Cardinals’ major league club as a catcher and reached what may have been the pinnacle of his athletic career in the World Series that year, which the Cardinals won in seven games over the Boston Red Sox. Playing in five games of the series, Mr. Garagiola got six hits in 19 at-bats, including four hits and three RBI in Game 4. He was 20 years old.

The rest of his career never matched the promise of his youth. In June 1950, he had a collision at first base with Jackie Robinson of the Brooklyn Dodgers. He fell hard, causing a separation of his left shoulder. Never again did he regain his old hitting form.

In 1949 Mr. Garagiola married Audrie Ross, the organist at the Cardinals’ ballpark. Besides his wife, he leaves two sons, Joseph Jr., a general manager of the Arizona Diamondbacks who became vice president of standards and on-field operations for Major League Baseball; and Steve, a sports broadcaster in Detroit; and a daughter, Gina Bridgeman, a writer in Arizona; and several grandchildren.

‘‘Each year I don’t play, I get better,’’ Mr. Garagiola wrote in his 1960 best-selling book ‘‘Baseball Is a Funny Game.’’ ‘‘The first year on the banquet trail I was a former ballplayer, the second year I was great, the third year one of baseball’s stars, and just last year I was introduced as one of baseball’s immortals. The older I get the more I realize that the worst break I had was playing.’’