Arsenal great Rice in hospital with cancer - reports
Rice, who was also caretaker manager of the 13-times English champions, joined the club in 1964 before retiring last year from his role as assistant to current boss Arsene Wenger.
"Our thoughts are with Pat and his family. Everyone at Arsenal sends him our best wishes," an Arsenal spokesman told the Daily Mail.
Rice, 64, made 528 appearances for the Gunners over 14 seasons after joining the youth team, going on to win the league and FA Cup double in 1971 and captaining the side to further FA Cup success in 1979. He also won 49 caps for Northern Ireland.
After a spell with Watford, he joined Arsenal as a youth team coach in 1984 before progressing to further coaching roles and enjoying great success as Wenger's assistant, winning seven trophies.
Wenger hailed the work of Rice upon his retirement in 2012.
"Pat is a true Arsenal legend and has committed almost his whole life to Arsenal Football Club, which shows huge loyalty and devotion," the Frenchman said at the time.
"I will always be indebted to him for his expert insight."
(Writing by Patrick Johnston; Editing by John O'Brien)