Congenital amusia is a lifelong musical disorder. It has been found that tonal-language speakers with amusia areimpaired in lexical tone perception. But it has also been found that tonal-language experience compensates the deficit in certainscenario, reducing prevalence rate of amusia in speakers of a highly complex tonal-language – Cantonese. Thus it remainsunclear whether lexical tone perception, especially its phonological processing, is impaired in Cantonese-speaking amusics.This study investigated the categorical perception of a continuum of lexical tone stimuli and pure tone analogues in Cantonese-speaking amusics and controls. The amusics showed reduced discrimination peak across the categorical boundary comparedto controls in lexical tone condition, suggesting impaired categorical perception; in pure tone condition, the amusics showedinferior performance on both between- and within-category discriminations, suggesting a deficit in auditory pitch processing.These findings indicate that phonological processing of tone is impaired in Cantonese-speaking amusics, despite possiblecompensation effect.