The purposes of this study were to investigate the levels of receptive and productive knowledge of English collocations of Thai EFL university students and identify the types of grammatical and lexical collocations reported as most and least known by the students. The participants were 286 third-year regular students affiliated with four academic faculties at a university in northeastern Thailand, in the academic year 2018. The participants' receptive and productive knowledge of collocations was measured through an acceptability judgment test and the collocation productive test. The results revealed that the participants' receptive and productive knowledge of collocations was at a low level; their receptive and productive collocation knowledge was significantly different at a .05 level. At the receptive level, their most known grammatical and lexical collocations were verb + preposition and verb + noun respectively. At the productive level, adjective + preposition and verb + noun were their most known grammatical and lexical collocations respectively. The findings highlighted the growing trend of world-wide English learners displaying a low level of collocation knowledge and implied urgent need of explicit instruction of collocations for EFL learners with an emphasis on the easier-to-understand collocation types.