This study investigated instructional delivery models and students' academic performance in senior secondary school Agricultural Sciences in Rivers State, Nigeria. The research work used pure experimental design (posttest only) with a population of 100 students and a sample size of 60 derived random sampling technique. The study was guided by four research questions and four hypotheses. The instrument for data collection was a teacher made performance assessment test (TMPAT) by the researcher with 20 items questions. The instrument was validated by three experts. Data analysis was done using mean and standard deviation and the hypotheses tested using t-test and ANOVA. Findings revealed that mastery learning and constructivist instructional delivery models improved students' academic performance more than lecture instructional delivery model. The information the findings illustrated the relationship between delivery method (an independent variable) and learner’s academic performance (a dependent variable). By employing bivariate means, it revealed that there was a connection between the delivery method and learner’s academic performance of (r)= 0.686. The paper therefore, recommended the use of mastery learning instructional delivery model, constructivist instructional delivery model and that the lecture instructional delivery model must be used in combination with other approaches to instructing students for effectiveness. Teachers were also encouraged to get training regular, employ improvisation in teaching and that teachers should allow their students generate ideas when using the constructivist instructional delivery model for better academic performance.