The International Journal Of Science & Technolodge 2017: Vol 5(10).Current perspectives on science education as well as the current curriculum policy in Tanzania stresses on the use of teaching methods that promote active engagement of learners during teaching and learning processes such the inquiry based approach. This study aimed at assessing the effectiveness of an inquiry-based approach on students’ conceptual understanding of genetics by comparing it with traditional or conventional style of teaching. The study used genetic as the case study to find out whether or not these two styles of teaching genetics would develop differently students’ science process skills. Inquiry-based approaches to science have been heavily emphasized by the newly adopted competence based curriculum in Tanzania. Two months (08weeks) were spent during the summer of 2015 in teaching themes within genetics at the selected schools in the vicinity of Morogoro Municipality. The study employed a quasi-experimental research design with pre and posttests. Eight (08) weeks genetics teaching courses were designed on the basis of both the inquiry based learning principles and conventional style. A genetics test of 25 items was used as a data collection tool in the pretest and posttest. Form six classes were taught using conventional method while form five classes in these schools had enough time and were taught using inquiry approach. Both classes had never been exposed to advanced level genetics. Independent samples t-test for experimental group (M = 21.73. s.d = 1.67) and that of control group (M = 21.87, s.d = 1.93), t (261) = 0.606, ρ = 0.545, α = 0.05. Hence, the null hypothesis, that there is no statistically significant difference in genetics posttest scores between the control and the experimental groups was accepted at 0.05 alpha levels. This means that there were no statistically significant difference in the effectiveness of inquiry-based (IBA) approach and the conventional method (TM) in enhancing the conceptual understanding of genetics content to students.