The present study investigates the impact of Task-Based Language Teaching (TBLT) on Iranian EFL learners' reading comprehension performance. Seventy participants were assigned randomly to the experimental and control groups. Having instructed the two groups with the same texts but different task types and activities (i.e., tasks in 4 types) during 20 sessions, the learners' reading performance results were compared through utilizing a reading post-test to both groups. The obtained data was analyzed using t-test to examine the effects of independent variable, namely, the method of teaching reading (task-based activities vs. classical reading comprehension) on learners' reading performance as the dependent variable. As well, the performance of the experimental group in four task types was analyzed in order to investigate possible differences among four reading sets of scores obtained on four task types. A follow up TUKEY test was also conducted to locate the exact areas of difference. Results showed that TBLT had a significantly more positive effect on learners' reading performance compared to the traditional reading instruction. Also, the second task type investigated in this study, namely reading, taking notes and discussing, was found to be more effective in increasing learners' reading skill. This study could have pedagogical implications for Iranian teachers and learners, because reading comprehension is a really important part of most instruction and examination systems in Iran.