The purpose of this research is to investigate the influence of trust to vendor to the online purchase decisions making mediated by perceived risk. The subjects of this research are students in UIN Sunan Kalijaga Yogyakarta who have been ever make online purchase decisions making. The number of subjects in this research are 76 students. The methodology of this research is quantitative research. The data are obtained using Online Purchase Decisions Making Scale, Trust to Vendor Scale, and Perceived Risk Scale. The data analyzed using product moment correlation test, multiple regression with causal step strategy and partial correlation. The result of this research are there are a positive effect between trust to vendor to the online purchase decisions making mediated by perceived risk with coefficient regression R= 0,687 and thre are direct effect c’= -0,025.