People often experience difficulties when they first hear a novel accent. Prior research has shown that relatively fast natural accent accommodation can occur. However, there has been little investigation of the underlying perceptual mechanism that drives the learning. The current study examines whether phonemic boundary changes play a central role in natural accent accommodation. Two well-established boundary shifting phenomena were used here--recalibration and selective adaptation--to index the flexibility of phonemic category boundaries. Natural accent accommodation was measured with a task in which listeners heard accented words and nonwords before and after listening to English sentences produced by one of two native Mandarin Chinese speakers with moderate accents. In two experiments, participants completed recalibration, selective adaptation, and natural accent accommodation tasks focusing on a consonant contrast that is difficult for native Chinese speakers to produce. We found that: (a) On the accent accommodation task, participants showed an increased endorsement of accented/mispronounced words after exposure to a speaker's accented speech, indicating a potential relaxation of criteria in the word recognition process; (b) There was no strong link between recalibrating phonemic boundaries and natural accent accommodation; (c) There was no significant correlation between recalibration and selective adaptation. These results suggest that recalibration of phonemic boundaries does not play a central role in natural accent accommodation. Instead, there is some evidence suggesting that natural accent accommodation involves a relaxation of phonemic categorization criteria.