Vocabulary knowledge is important to learners of any languages, for without vocabulary, one cannot speak, write or understand anything from the language being learned. Among different aspects of vocabulary learning, knowledge of collocations has a crucial role to decide the success of communication. The current study investigates the impact of collocation knowledge on English-majored students’ language skills at Can Tho University. This research was conducted with the participation of 269 English-majored students. The research tool was a collocation test with 45 items. Then, the collocation test scores and students’ scores of the listening, speaking, reading and writing from the previous semester were input in the SPSS software to figure out if there is any correlation. The research results reveal that students’ collocation knowledge was highly correlated with their achievement in the reading and writing skills. Implications are suggested for EFL teachers on how to help students improve their collocation knowledge.