The Giants said McCormick died Saturday at his home in North Carolina after a lengthy battle with Parkinson's disease.
"We are deeply saddened by the loss of Mike McCormick, a true gentleman and forever Giant," team president and CEO Larry Baer said in a statement. "Like many Giants fans, I have many fond childhood memories of watching Mike pitch at Candlestick Park and then was blessed to call him my friend these past 30 years.
"As a member of the inaugural San Francisco Giants team in 1958, Mike helped establish baseball on the west coast and then went on to play a major role in the legendary Giants teams of the 1960s, becoming San Francisco's first pitcher to win a Cy Young Award. ... He will be greatly missed by our Giants family and our thoughts are with Dierdre and the entire McCormick family."
McCormick played 16 years in the majors (1956-71) with the Giants, Orioles, Senators, Yankees and Royals. He compiled a 134-128 record with a 3.73 ERA in his MLB career and was a four-time All-Star selection.
McCormick signed with the Giants as a 17-year-old "bonus baby" in 1956 for $50,000, requiring him to skip the minors at the beginning of his career. He notched 50 wins before turning 23, becoming the youngest pitcher to hit that milestone until Dwight Gooden broke his mark in 1986.
He is survived by his wife, Dierdre; his children Tara, Mike Jr., Matthew and Stacy; six grandchildren and one great-granddaughter.