This study examined the Voice onset time (VOT) of Mandarin and English initial position stops as produced by native American-English speaking learners of Mandarin and also native speakers. The study primarily investigated the role of second language experience on native-like production of L2 VOT for the Mandarin stops /p, t, k, ph, th, kh/ and additionally examined any evidence for phonetic drift in the L1 English VOT as a result of L2 Mandarin learning and acquisition. To achieve this, the production of L2 Mandarin and L1 English by native AmericanEnglish speaking learners of Mandarin of two different levels of experience (beginner and advanced learners) were compared to that of monolingual Native speakers of Mandarin andEnglish. In total, thirty native American-English speaking learners of Mandarin, eight monolingual native Mandarin speakers, and eight monolingual American-English speakers participated in the study. Data was elicited via participants reading aloud prepared lists of Mandarin and/or English words. Statistical testing indicates that as a group beginner learners produced significantly different mean VOT than native Mandarin speakers for all six stops. In contrast, the advanced learner group's mean VOT only significantly differed with native speakers for /t/, indicating native-like VOT for the remaining five stops. Individual analysis of VOT data for L2 Mandarin long-lag stops /ph, th, kh/ showed that advanced (7 of 15) and even some beginner (3 of 15) participants were capable of producing native-like VOT for the whole set of long-lag stops and also that a number of participants were able to produce native-like VOT for some but not all of the long-lag stops. Logistic regression analysis examining the effect and influence of L2 experience and demographic related variables indicates only gender and Mandarin-speaking church missionary service to have a significant effect on native-like VOT probability with females and returned missionaries significantly more likely to achieve native-like VOT. Analysis of learner participants' L1 English VOT showed that for all three of the English long-lag stops (/p, t, k/), advanced learners of Mandarin produced significantly longer VOT than monolingual English speakers, indicating L1 phonetic drift in the form of assimilation towards the longer length of Mandarin long-lag stops. Significant difference was only found between beginner learner English VOT and monolingual VOT for /p/, suggesting instances of significant L1 drift increase when more L2 experience has been gained.