The study investigated the effect of discovery learning and problem-based instructional approaches on secondary school students' interest in Biology. Three research questions and four hypotheses guided the study. The study adopted the quasi-experimental design for the study. The population of the study was 753 senior secondary school year two (SS2) biology students in Oshimmili North local government area of Delta state. A sample of 159 SS 2 biology students was involved in the study. The

more »

... ment for data collection wasBiology Interest Scale (BIS)validated by lecturers in the Department of Science Education, Nnamdi Azikiwe University, Awka and Delta State University, Abraka and one experienced secondary school biology teacher. The reliability of BISwas established using Cronbach Alpha to be 0.93. Data collected by administering the instruments as pretest and posttest before and after treatment were analyzed using mean, standard deviation and analysis of covariance. The finding of the study revealed that there was significant difference between the mean interest scores of the students taught using discovery learning, problem-based instruction and conventional method in favour of discovery learning followed by problem-based learning. The study recommended that orientation and seminars should be organized by school administrators for biology teachers to aid them in the mastery of discovery and problem-based learning and how to integrate them in the learning process of biology.