This study aims to examine the influence of lexical tone upon voice onset time (VOT) in Mandarin and Hakka. Examination of VOT values for Mandarin and Hakka word-initial stops in different lexical tones revealed a significant influence. In Mandarin, stops' VOTs, ordering from the longest to the shortest, are in Tone 2, 3, 1, and 4, which conforms to Liu et al.'s (2008) results. However, it was found that the sequence results from the existence of non-words. Participants tended to pronounce non-words at a lower speed in order to produce them correctly. Therefore, data without non-words were further examined, in which no clear sequence had been found. For Hakka, Post-hoc tests show that aspirated stops in Tones 4 and 8 have significantly shorter VOT values than they have in other tones. The result suggests that future studies should consider the effect of lexical tone when studying in tonal languages.