Chinese learners of English often experience difficulty with English tense presumably because their native language is tenseless. We showed that this difficulty relates to their incomplete conceptual representations for tense rather than their poor grammatical rule knowledge. Participants made acceptability judgments on sentences describing two-event sequences that were either temporally plausible or misaligned according to verb tense (time clash). Both upper-intermediate Chinese learners of English and native English speakers were able to detect time clashes between events, showing that Chinese participants could apply tense rules explicitly. However, a predicted modulation of the N400 event-related brain potential elicited by time clashes in English-speaking participants was entirely absent in Chinese participants. In contrast, the same Chinese participants could semantically process time information when it was lexically conveyed in both languages. Thus, despite their mastery of English grammar, high-functioning Chinese learners of English failed to process the meaning of tense-conveyed temporal information in real time.