The 44 year old had just recently joined Roy Keane at Ipswich as a coach.
An Everton statement on their official website said: “Gary has always been a popular figure at Goodison, where he has forged a host of friendships through his time here as a player and a coach.
“An FA Cup winner as part of Joe Royle’s famous Everton side in 1995, he returned to Goodison in 2002 as a senior coach within the Blues’ Academy. He departed Goodison in 2006 to take up a position as reserve team boss for Liverpool but has maintained strong friendships on the blue half of the city.
“Our thoughts are with Gary and his family at this time.”
Liverpool also sent their best wished to Ablett with a message on their website: “Liverpool have been shocked and saddened to learn that Gary Ablett is facing a battle against cancer.
“The former Reds defender, who recently enjoyed a successful stint as reserve team coach, has been diagnosed with non-Hodgkin’s lymphoma after being taken ill last week.
“Everyone at the club would like to extend their best wishes to Gary and hopes that he makes a speedy recovery.”