This study investigated the efficacy of explicit lexical collocation instruction via the Corpus of Contemporary American English (COCA). To improve competence in lexical collocation and writing performance and to examine whether collocational competence and writing performance have a linear interrelation, 16 international English for Academic Purposes students received training on the use of the COCA interface. They were asked to first analyze the lexical collocations used in an academic paper, then search COCA for collocations to see how they are used pragmatically, and, finally, write an academic research paper on their own. A dependent t-test measured significant differences in performance, and the Pearson product-moment correlation coefficient identified the strength of the correlation between lexical competence and writing performance and their association with each other, respectively. The results showed that when students are given explicit instruction on how to utilize COCA to identify lexical collocations and their use in various contexts, both their lexical collocational competence and writing performance improves and, furthermore, these improvements correlate with each other. Implications for teaching lexical collocation are also discussed.