The Nile monitor is believed to have escaped at some point on Sunday night from a house on Netherby Road while his owners are on holiday.
A picture has been released of the lizard, but his owners say he is much bigger than the photograph suggests and is around 5ft from head to tail.
Mark Purcell is currently on holiday in Tenerife but received a call from a friend who has been feeding his lizards the Nile monitor, named Ni, had escaped.
It is still unclear how he escaped, as the enclosure door was not open, and Mark's other lizards are all still safe, with no signs of a break-in.
Mark said: "He isn’t aggressive in any way, he would be more scared.
"He isn’t going to last long outside, he needs to be near water.
"I am heartbroken, I lost one last year that I had for 16 years before he died."
Mark bought the lizard a year ago and says there would be a reward for anyone who comes forward with information.
Anyone with information can contact email@example.com and the information will be passed on.