This article reports the results of a study that explored Thai EFL learners' repertoire of congruent and incongruent academic English (L2) collocations in relation to their native-Thai language (L1) and academic experience. Eighty Thai tertiary students performed a gap-filling translation test on 15 congruent and 15 incongruent collocations by providing equivalent L2 collocates. The results indicated that the students' greater exposure to academic discourse increased their acquisition of academic collocations. However, overall they demonstrated insufficient knowledge of academic collocations, especially incongruent L1-L2 combinations. This is because they depended heavily on their L1 lexicon and general L2 lexis to compensate for their lack of knowledge and awareness of typical academic L2 collocations. The results suggest that although L2 exposure has a facilitative effect on collocation acquisition, it is still imperative that EFL learners receive explicit instruction which is devoted to elaborating and disambiguating the L1 and L2 meanings of academic collocations and their component words in isolation.