The study investigated gender difference on the impact of Activity-Based Instructional Strategy on students’ academic performance and retention in Agricultural Science among senior secondary school students in Imo state. Two research questions and two hypotheses guided the study. The study adopted a quasi-experimental design. The sample for the study comprised 118 Senior Secondary School two (SSS II) students that were drawn from two schools in Owerri Zone of Imo State. The instruments used for data collection were titled Agricultural Science Achievement Test (ASAT) and Agricultural Science Retention Test (ASRT). The instruments were validated by two (2) experts in the field of test and measurement. A reliability coefficient of 0.82 and 0.84 through Cronbach alpha method was obtained for ASAT and ASRT respectively. It was found out that female students exposed to Activity-Based Instructional Strategy had a significantly higher mean performance and retention scores than their male counterparts in the same group. In conclusion, Activity-Based Instructional strategy facilitates effective learning of Agricultural Science concepts. Based on these findings, it was recommended among others that, the teaching of Agricultural Science should be conducted in such a way that students effectively learn and retain the concepts presented to them and that the use of the Activity-Based Instructional Strategy seems to be relevant in achieving this goal hence, it should be incorporated into the teaching of Agricultural Science at the secondary school level.