The purposes of this study are to adapt and modify RFS (Religious Fundamentalism Scale) and IFS (Intratextual Fundamentalism Scale) in order to develop ISFS (Islamic Fundamentalism Scale). Moreover, this study is to find the coefficient correlation between IFS and prejudice towards Christians. Data were derived from 311 Muslim participants who were given a questionnaire. The results show that the items coefficient reliability of the ISFS is .86 and the items coefficient validity is between .37 and .64. Therefore, the ISFS is considered effective enough as an Islamic fundamentalism measuring tool. The research results also indicate that there is significant correlation between Islamic fundamentalism and prejudice towards Christians. Further, this research exhibits the Islamic fundamentalism as an independent variable in prejudice prediction towards Christians. Recommendations for further researches are about the relationship between Islamic fundamentalism and prejudice towards other believers, certain races and or ethnicities, homosexuals, and other psychological variables such as social identities, social dominance orientation, and authoritarianism in prejudice.