He was 67.
The band confirmed the news on Monday with a statement on its website.
"Glenn fought a courageous battle for the past several weeks but, sadly, succumbed to complications from Rheumatoid Arthritis, Acute Ulcerative Colitis and Pneumonia."
"Words can neither describe our sorrow, nor our love and respect for all that he has given to us, his family, the music community & millions of fans worldwide," read the statement.
The musician had been battling intestinal issues that also made the band to postpone its Kennedy Center Honours.
Frey co-wrote and sang a number of famous hits including Take It Easy, Lyin' Eyes and also lent his creative talents to Hotel California and Desperado. Calling him the 'spark plug', Eagles drummer and vocalist Don Henley said Frey was like a brother to him, according to a entertainment portal.
"He was like a brother to me; we were family, and like most families, there was some dysfunction. But, the bond we forged 45 years ago was never broken, even during the 14 years that the Eagles were dissolved."
"We were two young men who made the pilgrimage to Los Angeles with the same dream."
"...But, Glenn was the one who started it all. He was the spark plug, the man with the plan. He had an encyclopedic knowledge of popular music and a work ethic that wouldn't quit. He was funny, bullheaded, mercurial, generous, deeply talented and driven."
"He loved his wife and kids more than anything. We are all in a state of shock, disbelief and profound sorrow...Rest in peace, my brother. You did what you set out to do, and then some," Henley's statement read.
Born in Detroit on November 6, 1948, Frey met Henley in 1970. The duo was hired by Linda Ronstadt as part of a backup band, inviting them to tour with her in 1971.
Later, along with Randy Meisner and Bernie Leadon they went on to form the Eagles.
In 1980, the band broke up after Frey and Don Felder, publicly feuded during a concert. They reunited in 1990. The group was inducted into the Rock & Roll Hall of Fame in 1998.
Frey embarked on a successful solo career, enjoying a series of hits in the 80s, the biggest of which were tied to the soundtracks of Beverly Hills Cop and Miami Vice.
He was inducted into the Songwriters Hall of Fame in 2011, and released what would be his fifth and final solo LP, After Hours, in 2012.
Frey is survived by his wife of 25 years, Cindy, and their three children: Taylor, Deacon and Otis.
Photograph: Lisa Blumenfeld/Getty Images
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