Abstract: This study investigated the relative effects of demonstration and videotape mediated instructional strategies on Nigerian Secondary School Students� achievement and retention in Yoruba Language. The purpose was to find which of demonstration and demonstration with videotape mediated instructional strategies will influence better performance of students in Yoruba Language. The study employed the quasi-experimental pretest, posttest, control group design whereby three groups were assigned into treatment and control groups and they responded to pretest, posttest and retention test administered on them. The sample consisted of 135 junior secondary class two students selected from three secondary schools used for the study. The stratified random and cluster sampling techniques were used to select the sample. The research instrument used for the study was the Yoruba Language Achievement Test (YLAT) developed and validated by the researcher and administered on the subjects. The instrument was administered as pretest, rearranged and administered as posttest and was administered two weeks after that as retention test. The data collected were analysed using ANOVA, ANCOVA and the t-test. Three hypotheses were generated and tested at 0.05 level of significance and the results showed that both instructional strategies were significantly effective in the learning of Yoruba Language. The findings also show that the demonstration with videotape mediated instructional strategy was more significantly effective than the demonstration method alone. The findings also showed this same pattern of effectiveness on retention.