The instruction of Lexical Bundles (LBs) has been a challenging issue in language teaching. This study strived to determine the effect of the instruction of LBs on IELTS candidates’ performance on IELTS writing task 2. To this end, first, 100 male and female IELTS candidates were randomly selected from among 150 English learners as participants. Second, these participants were assigned to the experimental group and the control group, each with 50 learners. Both groups were then administered IELTS writing task 2 as a pretest. The experimental group was provided with ten sessions of instruction on LBs. The control group, however, did not receive any instruction. Finally, the researchers administered IELTS writing task 2 to both of the groups anew as a posttest. The results suggest that teaching the relevant bundles had some positive impacts on IELTS candidates’ general performance of the relevant writing tasks, grammatical range and accuracy, vocabulary knowledge, as well as observing cohesive ties and coherence in their writing. The results may provide some useful insights regarding the instruction of LBs in IELTS preparation courses Manuscript profile