Variation in pronunciation of vowels across American English dialects often creates the strongest distinctions between dialects and leads to lexical ambiguity between minimal pairs within dialects. This lexical ambiguity is stronger for listeners with lifetime exposure to multiple dialects than to a single dialect. In the current study, we investigated the influence of brief, in- lab dialect exposure on lexical competition and perceptual adaptation. Midwestern American English participants were first presented with a familiarization short story told in one of two unfamiliar dialects (Southern American English or a novel accent) and then completed a visual-world eye-tracking task containing both acoustically ambiguous and non-ambiguous words from each dialect in a forced-choice task. The results showed evidence of greater lexical competition for target dialect minimal pairs following familiarization. This pattern of results is consistent with previous work suggesting greater lexical competition following lifetime exposure to dialect variation among geographically mobile listeners, suggesting similarities in the effects of brief in-lab and lifetime exposure to dialect variation on lexical competition and processing.