The purpose of this mixed-method investigation was to examine the effect of explicit instruction of cognitive strategies on the reading performance of Iranian graduate students and identify the cognitive strategies the participants used while reading a scientific article in English (L2). Prior to the study, the students completed a questionnaire and took part in a semi-structured interview providing information on the reading strategies they used while reading English texts. In order to also identify the participants' improvement in reading English texts, they completed the reading section of the IELTS test prior to and following the treatment. During a 16-week course, students became familiar with cognitive strategies through explicit instruction. At the end of the course, the students were required to read a scientific article in English and think-aloud in order to identify the reading strategies they employed while reading. The quantitative results (paired-sample T-test) revealed that the participants' reading comprehension significantly improved after explicit instruction of cognitive strategies. The qualitative data (think-aloud protocols) indicated that the participants used more cognitive strategies while reading scientific articles in English after receiving explicit instruction. Pedagogical implications are provided for further research.