Motivation is force used within the educational setting to encourage student learning and understanding. Motivation and achievement have long been recognized to have a close cause effect relationship on ability and achievement. The anticipated relationship is that, the higher the motivation ability the higher the expected level that is why the issue of motivation of students and the impact of academic performance are considered as important aspects of effective learning. Based on this background, this research investigated the effect of motivation on the academic achievement and interest of students in secondary school biology in Makurdi metropolis. Five schools were randomly selected from among the secondary schools in Makurdi metropolis. The study made use of a quasi-experimental design of the equivalent control group. The finding revealed that the students taught using motivation achieved more and those taught without motivation achieved less. Both male and female students exposed to motivational approach performed competitively better in the achievement test. There was also no significant difference in the mean interest rating of male and female students. This study has therefore shown that biology is one of such areas where the use of motivation may be beneficial.