The current study aimed to investigate the effects of metacognitive strategy instruction on reading strategies and reading comprehension of undergraduate students. To this end, a quasi-experimental design with two groups of 54 non-English major students at a Mekong Delta's university in Vietnam was employed. The treatment that consisted of eight 50-minute metacognitive strategy instruction sessions guided by the CALLA was intervened into weekyl lessons for the experimental group, while the conventional method of reading was applied for the control group. A pre-and post-survey revealed a significant increase in metacognitive awareness after the intervention. The results of two reading comprehension tests (pretest and posttest) also showed a significant increase in the mean scores of the experimental group, which indicated a positive effect of metacognitive strategy instruction on the students' reading comprehension achievement. The in-depth analysis of the difference indicated that there was a positive correlation between metacognitive strategy use and students' reading outcome after the intervention. The findings provide some crucial pedagogical implications for teaching reading to EFL learners.