This research investigated the effects of conventional and demonstration methods on teaching and learning of secondary school Chemistry in Ikere local government area of Ekiti State. The design of this study was the quasi-experimental research design. The population of the study was the entire senior secondary school two (SSS2) Chemistry students in all the public secondary schools in Ikere local government area of Ekiti State. SSS2 students are chosen because it is the class that is very close to preparation for external examination and that the topic introduction to organic chemistry to be taught are offered at Senior Secondary School II according to the new senior secondary school curriculum. The sample size for the study is fifty six (56) students in two (2) intact classes in the senior secondary school two (SSS2) class. The schools were randomly drawn from the ten (10) schools using simple random sampling by balloting without replacement. The instrument was the Chemistry Achievement Test (CAT) on the topic “ introduction to organic chemistry”. The test –retest method of reliability was used to establish the reliability index of the instrument. The reliability index obtained was 0.79 at 0.05 significance level. This showed that the instrument was reliable for the study. Frequency counts and percentage were used in analyzing the personal data of respondents. While the research hypotheses were tested using the t-test and analysis of covariance (ANCOVA) at 0.05 level of significance. The findings of the study indicated that there is no significant difference between Chemistry achievement scores of students taught with demonstration method and those taught with conventional method prior to the experiment; there was a significant difference between the performance of students taught with conventional method and those taught with demonstration method after the experiment; the mean performance gain of student taught with demonstration strategy was higher than that of those taught with conventional method; there is no significant difference between the posttest scores of male and female students taught with conventional method and those taught with demonstration method; and the mean performance gain of male and female students taught with demonstration strategy was higher than that of those taught with conventional method but this increment was not due to students’ gender. Based on the findings, appropriate recommendations were made.