The study investigated the effect of teachers' instructional methods on students learning outcomes in selected senior secondary school in Kaduna, Nigeria Two instructional methods (Demonstration and Lecture) were used on target population of one thousand nine hundred and eleven (1,911) senior secondary (S.S. II) Science Students. The sample consist of 100 Students randomly drawn from two co-educational senior secondary schools within Kaduna North LGA. The students were divided in to two groups: The experimental group and the control group of 50 students each based on a categorization test to ascertain the equivalence of the group. The pretest-posttest quasi-experimental control group design was adapted. The students in the experimental group were exposed to Demonstration Method, while those in the Control group were exposed to the lecture instructional strategy for a period of three weeks. The instrument developed and validated for data collection was Chemical Bonding Performance Test (CBPT). Four research questions were stated and four null hypotheses were tested. The data collected were analyzed using mean, standard deviation, t-test and ANOVA at 0.05 level of significance. The major findings from the study shows that there is significant difference in learning outcome on students exposed to demonstration and lecture strategies used to teach chemistry (t[subscript cal] = 0.774 >t[subscript crit] = 0.443 and F[subscript cal] = 0.771 > F[subscript crit] = 0.710 at P<0.05) and there is no significant difference in the academic performance of both male and female students exposed to demonstration instruction in teaching chemistry (t[subscript cal] = 0.177 < t[subscript crit] = 0.861 and F[subscript cal] = 0.728 < F[subscript crit] = 0.781 at P<0.05) . Findings from present study suggest that Chemistry teachers should incorporate demonstration method for teaching at senior secondary school level so as to enhance academic performance and also Curriculum planners should recommend and ensure demonstration method is used for teaching chemistry at senior secondary school among others.