McCain, who was severely injured after his plane was shot down over North Vietnam in 1967, spent more than five years as a prisoner of war.
He was later elected to the House of Representatives in 1982, the Senate four years later and made an unsuccessful bid against Barack Obama in the 2008 Presidential Election.
McCain was a fan and longtime supporter of the Arizona sports teams, including the Cardinals.
"Your legacy in our state and country will forever live on. May you rest in peace, Senator John McCain. Our thoughts are with all of @SenJohnMcCain's family and friends," the Cardinals posted on Twitter.
Cardinals president Michael Bidwill said that "the world will never be the same" without McCain's voice.
"We are heart-broken by [McCain's] passing but know that the character, courage and conviction that he demonstrated throughout his life will forever endure," Bidwill wrote.
Fitzgerald, who penned a tribute to McCain for Sports Illustrated in December, also took to social media to honor his "dear friend."
Rest in peace to an American hero, statesman, servant of the people, and dear friend. Godspeed Senator McCain. My prayers for Cindy and the beautiful McCain family. pic.twitter.com/Tj87Hb8MtY— Larry Fitzgerald (@LarryFitzgerald) August 26, 2018
"Rest in peace to an American hero, statesman, servant of the people, and dear friend," he wrote. "Godspeed Senator McCain. My prayers for Cindy and the beautiful McCain family."
Fitzgerald visited McCain in February in the wake of the latter being diagnosed with glioblastoma, an aggressive form of brain cancer.
Cindy McCain shared a picture on her Instagram account of the three of them at the cabin in Cornville (Ariz.), where the elder McCain had been receiving medical treatment.
Former Cardinals head coach Bruce Arians also tweeted a special message.
"Senator John McCain-Gone but never forgotten. A true American hero. RIP my friend!" Arians wrote. "One of my proudest moments as @azcardinals head coach was standing with you for our National Anthem."