Congenital amusia is a neuro-developmental disorder of pitch processing. This study investigated how this deficit affects lexical tone perception with and without context. Twenty-three Cantonese-speaking amusics and 23 controls were tested on the identification of high-variation tone stimuli in isolation vs in a carrier sentence. The controls generally achieved a higher accuracy with context than in isolation, suggesting that speech context facilitated tone identification. In contrast, amusics generally failed to benefit from the context, despite some variation among different tones. These findings provide insights into the underlying deficits of amusia, revealing a context integration deficit of tone perception in amusia.