The study examined the Effects of Constructivists Approach on Performance and Retention of Genetics Concepts among Secondary School Students in Sokoto State, Nigeria. Quasi experimental research design was adopted which involves pre-test, post-test and post-posttest on two non-equivalent groups designated as experimental and control group. Two research objectives and questions guided the study while two null hypotheses were tested at 0.05 level of significant. The population of the study consisted of 1,639 SS II students across the 10 Schools under Science and Technical Education Board in Sokoto State. Multistage sampling techniques was used to select the sample for the study, 237 SS II students were selected from four schools using intact classes. Genetics Performance Test (GPT) instrument which contained 30 items were used to collect data. The instrument was validated by experts in the field of Biology. Pilot testing was used to establish the reliability of (GPT), the reliability coefficient of 0.86 was obtained using (KR-20) formular. The independent t-test was used to test the two null hypotheses. The findings of the study revealed that there is significant difference in the performance and retention of students taught genetics using constructivists approach than those taught using conventional method. Based on the findings, it was recommended among others that, Biology teachers should be encouraged adopt constructivist approach to engage the students in meaningful learning which led to enhanced performance of secondary school students in Genetics.