This study assessed demonstration method for teaching Islamic Studies at upper basic schools in Kwara State. Quasi experimental research design was used in this study. The population for this study comprised all upper basic students of Islamic Studies in Kwara State. Multi stage method of sampling was adopted in the study. A fifty multiple choice questions were adapted from Basic Education Examination Certificate (BECE) and lesson plane designed on al-Adhan (calling prayer), al-Iqāmah (commencement of prayer), Salātul Jamā’ah (congregational prayer) and Islamic greeting were used as an instrument in the study. Descriptive statistic tools such as percentage, mean and standard deviation were used to describe demographic data of the participants and answer the research questions raised in the study. ANCOVA was the inferential statistical tool used for testing hypotheses generated in the study. It was discovered in the study that 48.4% and 51.6% were the population of male and female participants used in the study. This indicated that the percentage of female participated in the study was higher than their male counterpart. The findings of the study revealed that demonstration method is one of the effective methods of teaching Islamic Studies in upper basic schools in Kwara State because of the mean scores of 56 which denoted strong effectiveness. The findings of the study also revealed that there is significant effect of demonstration method on upper basic students’ academic achievement in Islamic Studies in Kwara State. It however, discovered that there was significant effect of gender (moderator variable) and demonstration method on upper basic students’ academic achievement in Islamic Studies in Kwara State (F_{(2, 63) =} 11.668, p˂0.05). It concluded that demonstration method is highly effective for teaching Islamic Studies in upper basic schools in Kwara State. The study, therefore, recommended that upper basic Islamic Studies teachers should be trained on how to effectively use demonstration method for teaching.