Speaking proceeds under the constraint of time. While speaking, speakers are under constant pressure to follow the message being received and to formulate rapid responses to their partners. In the IELTS (International English Language Testing System) Speaking Test, the communicative nature of the interview creates an ideal situation for applicants to use impression management (IM) behaviors. Sixty IELTS students studying in Bahar institute of Shiraz, Iran were selected for this study and assigned to two groups of control and experimental. The experimental group received treatment and students were taught IM tactics. At the end of the course, students took part in the test and their oral proficiency was measured by a certified IELTS examiner. The interviews were also videotaped and the participants were asked to attend a post-test interview and to fill out a post-test questionnaire, too. The results proved the positive effect of IM instruction on candidates' performance in the IELTS Speaking test.