In the early part of the 21st century, marketing has been dramatically affected by the introduction of new digital marketing, which has been driven largely by improvement in technology and the ways customers interact with brands through new technology. The rapid development of high-speed mobile networks and mobile device technology have led to an immense growth of online video content. In this paper, we investigated online video marketing in social media as one of digital marketing channels that FMCG (fast moving consumer goods) companies in Vietnam are using to approach customers. The research adopted a typical case study of the leading dairy brand in Vietnam called Vinamilk with secondary data collection, which was aimed to advance knowledge on how the FMCG brands like Vinamilk are using online video marketing in their digital marketing strategy to increase engagement with Vietnamese customers and help drive brand awareness among them. This paper proposed some suggestions for FMCG businesses in Vietnam in online video marketing activities in order to increase brand awareness, brand trust and loyalty, boost engagement with customers and thus increase business efficiency