The study scrutinized the probable interaction between using cognitive test-taking strategies, reading proficiency, and reading comprehension test performance of Iranian postgraduate students, who studied English as a foreign language. The study also probed the extent to which the participants' test performance was related to the use of certain cognitive test-taking strategies. The participants were 343 MA students, who took an English reading comprehension test and answered a test-taking strategy questionnaire. The gathered data were subjected to a set of parametric statistical analysis, including descriptive statistics, factorial, and regression analyses. The results showed that the participants at the high level of reading proficiency used comprehending and retrieval strategies more frequently than did the participants at the intermediate and low levels. The findings reflected that 33% of the variance in the test performance was due to the use of cognitive test-taking strategies. Thus, the observed scores cannot account for the actual language ability of test takers. The findings can help language teachers gain a better understanding of the strategic process of test taking and improve the validity of language tests. In addition, the findings can assist language teachers in interpreting test scores from a different angle to make a sound judgment about the actual ability of language learners and decrease error of measurement. The findings also recommend language teachers to pay systematic attention to the linguistic and strategic aspects of language learning and adopt their teaching approaches to the needs of language learners to improve their reading ability.