Recent research in SLA indicates that collocations are an indispensable aspect of language learning. Its importance in learners' writing ability is, therefore, undeniable. Thus, the present study attempted to explore the effect of explicit teaching of collocations on learners' awareness and use of them in their writing. It differed from previous studies in that the main focus was on learning the collocations of the most important nouns. To this end, the present study used a mixed method approach with a pretest-treatment-posttest quasi-experimental design and qualitative analysis of questionnaire to investigate the questions. To collect data, an experimental and a control group were selected on the basis of the results of a proficiency test (PET). The participants were conveniently chosen as samples from a grand total of 58 students. The learners were further randomly assigned to two groups: one experimental group and one control group. The participants in the experimental group (N = 15) received weekly interventions based on explicit teaching of collocations but the control group (N = 15) received no instruction regarding collocations and had their regular procedure. The results of independent and paired sample t-tests (sig < 0.05) indicated that there was a significant difference between the two groups' performances in the achievement collocation test. Thus it can be concluded that teaching English collocations to EFL learners and raising their awareness will enhance their proficiency in writing and improve their collocational competence. The qualitative analysis of the responses to questionnaire also supported a positive impact of the method on students' fluency in writing.