This study aims to examine the effect of social media advertising, trust, and electronic word-of-mouth (eWOM) on the online shopping behavior of Egyptian millennials. It also aims to investigate the moderating effect of the demographic characteristics on the examined variables. To fulfill the research aim, both quantitative and qualitative approaches are used. The quantitative approach consists of an online survey that is conducted to collect data on consumers' perceptions toward social media advertising, trust, eWOM, and online shopping behavior. The sample consists of 517 respondents based on convenience sampling. The qualitative approach consists of four interviews with the Store Managers of well-known fashion brands in Egypt to collect data on sellers' perceptions of online shopping behavior. The quantitative analysis shows that social media advertising, eWOM and trust have significant positive effects on online shopping behavior. However, when examining the effect of demographic characteristics (age, gender, educational level, and income level), the results reveal that millennials with varying demographic characteristics show varying effects of social media advertising, trust, and eWOM on online shopping behavior. The qualitative analysis shows that social media advertising affects brand image and positively affects sales. This study contributes to the field of electronic marketing and provides insights to a knowledge of consumer behavior in an online environment, while particularly advancing knowledge on the online shopping behavior of Egyptian millennials.