[3] Fidrych joined the Tigers spring training camp in 1976 and made the roster, though he did not make his Major League debut until April 20, pitching only one inning through mid-May.

In his third appearance, on May 15, Fidrych made his first major league start, caught by Bruce Kimm, his batterymate in 1975 at Triple A Evansville.

He held the Cleveland Indians hitless through six innings and ended up with a two-hit, 2–1 complete game victory, with one walk and five strikeouts.

Four days later in Minnesota, before Fidrych's thirteenth start, the Twins released thirteen homing pigeons on the mound before the game.

On Saturday, July 24, Fidrych surrendered four earned runs on nine hits and lasted only 41⁄3 innings; John Hiller got the win for the Tigers in long relief on the Game of the Week.

Fidrych recalled: "He (NBC commentator Tony Kubek) said, it looked like you were gonna cry.

"[27] The next day, Fidrych received a telegram informing him he had been fined $250 by baseball commissioner Bowie Kuhn; however, it was a prank sent by his own teammates.

Six days later, the Tigers drew a season-high 51,822 fans as Fidrych went to 14–4, beating opposing pitcher Frank Tanana 3–2.

[31] During the offseason between the 1976 and 1977 seasons, Fidrych published an autobiography with Tom Clark titled No Big Deal.

Still on the disabled list toward the end of the season, Fidrych worked as a guest color analyst on a Monday Night Baseball telecast for ABC; he was subsequently criticized for his lack of preparation, as when play-by-play partner Al Michaels tried talking with him about Philadelphia Phillies player Richie Hebner and Fidrych responded, "Who's Richie Hebner?

Fidrych pitched his last MLB game on October 1, 1980, in Toronto, going five innings and giving up four earned runs, while picking up the win in an 11–7 Tigers victory which was televised in Detroit.

At the end of the 1981 season, Detroit gave Fidrych his outright release and he signed as a free agent with the Boston Red Sox, playing for one of their minor league teams.

Dr. Andrews discovered the torn rotator cuff and operated; still, the damage already done to the shoulder effectively ended Fidrych's chance of coming back to a professional baseball career.

Teams started asking Detroit to change its pitching rotation so Fidrych could pitch in their ballparks, and he appeared on the cover of numerous magazines, including Sports Illustrated (twice, including once with Sesame Street character Big Bird),[41][42] Rolling Stone (as of 2015, the only baseball player ever to appear on the cover of the rock and roll magazine), and The Sporting News.

"[43][44] Fidrych also drew attention for the simple, bachelor lifestyle he led in spite of his fame, driving a green subcompact car, living in a small Detroit apartment, wondering aloud if he could afford to answer all of his fan mail on his league-minimum $16,500 salary, and telling people that if he hadn't been a pitcher, he'd have been happy pumping gas in Northborough.

[45][46][47][48][49] At the end of his rookie season, the Tigers gave him a $25,000 bonus and signed him to a three-year contract worth $255,000.

[50] According to the Worcester County District Attorney's Office, a family friend found Fidrych dead beneath his ten-wheel dump truck at his Northborough home around 2:30 p.m. on April 13, 2009.

[51] Authorities said Fidrych suffocated after his clothes had become entangled with a spinning power takeoff shaft on the truck.

[52] Joseph Amorello, owner of a road construction company who had occasionally hired Fidrych to haul gravel or asphalt, had stopped by the farm to chat with him when he found the body underneath the dump truck.

[2] A 2012 wrongful death suit filed by Fidrych's widow was dismissed by a Massachusetts appeals court in November 2017.

[54] In a unanimous decision, the court ruled that the companies in question did provide warnings and that their equipment was free of design defects.

On April 15, 2009, the Tigers paid tribute to Fidrych at Comerica Park with a moment of silence and a video before their game against the Chicago White Sox.

[58][59] On June 19, 2009, Jessica Fidrych honored her father at Comerica Park by throwing out the ceremonial first pitch to manager Jim Leyland for the Tigers game against the Milwaukee Brewers.

[61] The Varsity Baseball Field at Algonquin Regional High School is named in honor of Mark Fidrych.