Lexical access is highly contextual. For example, vowel (rime) information is prioritized over tone in the lexical access of isolated words in Mandarin Chinese, but these roles are flipped in constraining contexts. The time course of these contextual effects remains unclear, and so here we tracked the real-time eye gaze of native Mandarin speakers in a visual-world paradigm. While listening to a noun classifier, before the target noun was even uttered, gaze to the target noun was already greater than looking to phonologically unrelated distractors. Critically, there was also more distraction from a cohort competitor (tone information) than a segmental competitor (vowel information) in more semantically constraining contexts. Results confirm that phonological activation in Mandarin lexical access is highly sensitive to context, with tone taking priority over vowel information even before a target word is heard. Results suggest that phonological activation in real-time lexical access may be highly context-specific across languages.