This study investigated the effect of Know-What-Learn (KWL) on senior secondary school students' academic achievement in reading comprehension. The study adopted a quasi-experimental design - specifically a pretest posttest non-equivalent control group design. Two research questions and one hypothesis guided the study. The sample was made up of 80 students. The instruments for this study were 25 items multiple-choice reading comprehension achievement test. Mean and standard deviation were used to answer the three research questions while ANCOVA was used to test the hypothesis at p < 0.05. The result revealed that students taught using KWL had a higher academic achievement gain score than those taught using lecture method. Based on the findings, some recommendations were made which include that English language teachers should be trained and versed on how best to develop and use KWL strategy so as to achieve their objectives of enhancing academic achievement in Reading comprehension.