This study aims to determine how brand ambassador, trust, website quality and vendor reputation influence online purchase decisions at Tokopedia Marketplace. This study is a quantitative study with brand ambassador, trust, website quality, vendor reputation and purchase decision as the variable. The population used in this study was collage students at three universities in Purwokerto. The sampling technique used in this study was by purposive sampling method that generated 102 respondents. This study’s analysis techniques were descriptive analysis, instrument test, classical assumption test, multiple regression analysis and hypothesis testing. The simultaneous test showed that brand ambassador, trust, website quality and vendor reputation positively and significantly affect purchasing decision. In contrast, vendor reputation has a positive and significant effect on purchasing decision, trust has a positive but not significant on purchasing decision, while brand ambassador and website quality has no effect on purchasing decision.