The present study was conducted to explore the impact of explicit collocation instruction on the ESL learners' writing ability. Furthermore, this study was an attempt to find if there is any significant difference between male and female learners on their use of collocations in writing tasks. In so doing, 63 advanced English as a Second Language (ESL) learners (35 male and 28 female) who were studying English at the University of North Carolina at Charlotte were conveniently sampled. At first, all participants received a writing pretest; then, they were divided into two groups randomly, experimental group and control group. The experimental group received explicit collocation instruction in writing class for seven sessions, while control group was taught using conventional techniques for writing. Finally, both groups received another writing posttest. Data were collected numerically and statistical analysis was used to show the difference between the two groups at the end of the study. The obtained data were analyzed using independent samples t-test procedures. The results indicated that collocation instruction has impact on writing ability of learners. In addition, it was found that no significant difference between male and female learners in their use of collocations in writing tasks could be seen.