World Boxing Union welterweight champion Eamonn Magee said he was devastated at the theft of his title belt from his mother's home.
Eamonn Magee has appealed for return of his title belt
The diamond-studded belt, worth thousands of pounds, was taken from the house at Holmdene Gardens, north Belfast.
Mr Magee, 33, successfully defended his title in March after suffering multiple injuries in an attack last year.
He said the belt had value to him, but "was useless to anyone else".
The black leather belt was decorated with a gold crest surrounded by diamonds and carried the number 49.
"I just appeal to the intruders to bring it back, no action will be taken," he said.
Doctors told Mr Magee he would never fight again because his injuries were so severe.
However, he went back into training and won his comeback fight against Danish boxer Allan Vester.
He said he hopes to defend his title in the King's Hall, Belfast, in October.