This is the first empirical ecological study on the critically endangered Yellow-crested Cockatoo (Cacatua sulphurea) in a nonnative urban habitat of Hong Kong, southern China. The exotic Hong Kong population creates a conservation paradox in which efforts toward protecting the endangered species would conflict with the preservation of recipient communities and habitats. The diet and feeding ecology of Yellow-crested Cockatoo were investigated to better understand the interaction between the exotic population and its inhabiting urban environment. The results indicated that the cockatoos mainly exploited 11 plant species and 4 food types, most of which were exotic plant species. They had a moderate Levin's niche breadth of 0.41, suggesting that the birds were generalist feeders with flexible diet in a nonnative urban environment. They preferred to feed solitary or in small flocks, consistent with the low conspecific attraction rate in feeding. Conspecific attraction might increase the foraging efficiency of Yellow-crested Cockatoo. Cotton tree (Bombax ceiba) was ecologically significant to Yellow-crested Cockatoo; it not only provided the birds with different food types throughout the year, but also served as the major venue for take-away food. Our findings will help bridge the knowledge gap in the feeding ecology of urban exotic parrots and provide valuable information on how to manage or conserve the endangered alien species.