In the present study, I evaluated whether ESL teachers could teach students three reading metacognitive strategies (planning, monitoring, and evaluating) and whether improving knowledge of these strategies would improve their reading comprehension. According to the research findings and in light of the hypotheses, two conclusions come to the surface. First, although the teacher, not the researcher, taught the three strategies, and the students might have learned these strategies in their first language, the subjects’ metacognitive knowledge increased on the three MARSI reading scales. Thus, teachers can effectively teach metacognitive strategies. Second, an increase in metacognitive knowledge does not necessarily lead to improvement of reading comprehension. A reading intervention of planning, monitoring, and evaluating is not always strongly linked to improving readers’ comprehension due to other variables or factors such as sample size, duration of training, research design, and students’ motivation.