News of Miller’s condition emerged in November and he had been receiving treatment in the United States, where he ended his playing career with Wilmington Hammerheads in North Carolina.
“Everyone at CelticFC is deeply saddened to hear of the passing of former midfielder Liam Miller,” Celtic, whose players will wear black armbands for Saturday’s Scottish Cup tie against Partick Thistle, said in a statement.
“Our thoughts and prayers are with his family and friends at this time.”
Miller made his Celtic debut in 2000, but made his name by scoring twice in the Champions League in the 2003-2004 season which attracted United’s interest.
“Manchester United is deeply saddened to learn of the tragic death of our former midfielder Liam Miller,” United said in a tweet. “We extend our condolences to his loved ones at this extremely difficult time.”
“I’m deeply saddened to hear of the passing of my friend and old team mate Liam Miler,” said former Celtic midfielder Stiliyan Petrov, who himself has battled leukemia.
“My thoughts and prayers are with his family and friends. RIP my friend.”
After making 22 appearances under Sir Alex Ferguson at Old Trafford, a nomadic career took Miller to Sunderland, Queens Park Rangers and Hibernian before a three-year spell in Australia with Perth Glory, Brisbane Roar and Melbourne City.
He returned to his native Cork in 2015 to join Cork City before a final season with the Hammerheads in 2016.
“Our thoughts are with Liam’s family… Rest In Peace,” former United midfielder David Beckham posted on Instagram.
Miller also won 21 caps for the Republic of Ireland at international level.
