Nowadays, more and more people spend their time shopping through online marketplace instead of going to the mall or any other department stores. In this case, Tokopedia as one of the biggest online marketplace in Indonesia will be the topic of this paper. To what extend will people decideto purchase their product through Tokopedia. For this reason, this research are conducted to find out the effect of web design, brand ambassador and the promotion of Tokopedia towards the customers purchasing decision which is why the quantitative data from 250 respondent which live in Indonesia and ever shops in Tokopedia are collected using online questionnaire in the form of non-probability sampling. This quantitative data is then analysed using the structural equation method (SEM) based on the previously collected quantitative data. The result shows that 3 out of5 hypotheses being accepted, while the other 2 being rejected, with most of the dimensions of easeof use, security and privacy of a website design and promotion having the most positive influence, withbrand ambassador and web design having the least positive influence.