Nurturing critical thinking (CT) has been acknowledged as a core objective of tertiary education, and drawn attention from academia of teaching English as a Foreign Language (EFL) in China. The thrust of the present study was to determine the association between CT and EFL argumentative writing among Chinese undergraduates. To this end, 110 English majors across three grades at two universities were conveniently selected and given the critical thinking skills (CTS) test and EFL argumentative writing test. The results of this study indicated that undergraduate English majors in China did not possess strong CTS. Though their CTS was not found to be significantly correlated with EFL argumentative writing performance, textual analysis of typical essays showed that strong-CTS learners outperformed weak-CTS ones in relevance, clarity, logicality, profundity and flexibility of argumentative writing. The obtained results suggest a need to integrate CT into EFL writing instruction.