The purpose of this study was to analyze the marketing mix, interface, and trust affecting online purchase decision by consumers in Bangkok. The multi-stage sampling technique together with questionnaires were used to collect data from 400 consumers who had purchased products via online channels. Multiple regression was implemented to analyze the data. The results showed that most of the respondents were female with bachelor degree. Most of them worked in private companies and they had used the internet for 4-6 years between the hours of 18.00 pm. to 24.00 am. The results also revealed that the marketing mix factors affecting the online purchase decisions of consumers in Bangkok at the statistically significant level of 0.05 were the products and channels of distribution, the interface feature of company profiles, the trust in service and duration of customer attention. However, a) the marketing mix of pricing and promotion, b) the interface of product information, payment, purchase, return, and preview of product images, and c) the trust factors of reliability, truth, and comprehension had no effect on the online purchase decisions of consumers in Bangkok.