Introduction: Inquiry based method is one of the innovations in teaching techniques. Despite its benefits, inquiry based method has not got due popularity in the Pakistani context. Purpose: The objectives of the study were to examine the effects of Inquiry Based Method on the academic achievement of students Biology at secondary level, to compare the academic achievement of low-achievers of Biology at secondary level taught through inquiry Based Method and Lecture Method, and to compare the academic achievement of high-achievers of Biology of secondary level taught through Inquiry Based Method and Lecture Method. Methodology: Two null hypotheses were formulated in order to achieve the objectives. One hundred twenty (120) science students of grade 10th (2017-2018) from GGHS No. 2 Haripur were considered as population. Sixty (60) Science students of grade 10th from GGHS No. 2 Haripur were selected as sample of the study. These students were divided into two equivalent groups i.e. control (n=30) and experimental group (n=30) on the basis of mean scores of pre & post- test on Biology. Experimental group was taught through Inquiry Based Method and control group was taught by Traditional Lecture Method for eight weeks. Results: The analyzed data revealed that experimental group significantly performed better than the control group. Similarly, the lower achievers of experimental group showed significantly better performance than lower achievers of the control group. Recommendations: It was recommended that teachers who are teaching Biology at secondary school level may be trained to teach Biology by applying Inquiry group learning method.