Believed to be back home in Cork receiving treatment, former Hibs player Tam McManus tweeted that Miller: "was in the U.S. for treatment this month and flies back tomorrow to start chemo here".
"The news, we heard about it just recently, we didn't know how bad it was". We're unsure of all the details, but our thoughts go to his family.
Miller retired from playing previous year and had returned to Ireland with his wife and three children to complete his UEFA coaching qualifications.
Ex-England striker Chris Sutton said: "All thoughts and prayers go out to my old teammate Liam Miller tonight".
It was confirmed last night that former Celtic and Man United footballer Liam Miller, 36, is beginning chemotherapy this week to combat pancreatic cancer.
Miller won 21 caps for the Republic between 2004 and 2009, and current Ireland global David Meyler said the squad are thinking about their compatriot. "We are all thinking of him and his family and hope he can pull through and be strong".
"The thoughts and prayers of everyone at Celtic Football Club are with Liam Miller and his family at this time, ' read a tweet from the Scottish champions" Twitter account.