The paper analyzes VOT values in Serbian-English interlanguage phonology, as well as in the production by native American English speakers, with a special focus on the effect of speech style formality on the values of VOT. In order to answer the proposed research questions, the investigation included 72 first-year students at the Faculty of Philology and Arts, University of Kragujevac, whose plosive production was recorded in three tasks differing in the degree of formality: a word list, paragraph reading and an interview. The same tasks were performed by the native speakers, too. The obtained corpus was analyzed from the perspective of experimental phonetics accompanied by descriptive and qualitative interpretation of results. Speech style proved to be a statistically significant predictor of variation in VOT for all the plosives both among native and non-native speakers. The differences detectable among speakers are best represented by the values of VOT for both voiced and voiceless plosives, most often interpreted as a result of the differences in phonological systems of Serbian and English. The results of the paper underscore important pedagogical implications and expand the options for future research in the field of interlanguage phonology.