Internet-based social media has become a part of life of the public society in this era. Many people use Facebook, Whatsapp, LinkedIn, Blogs and other social media to interact to each other. With social media, people exchange information and share experiences in cyberspace. Furthermore, at the present, social media is already becoming a part of the organizational culture in work place. This study aimed to analyze the relationship between the culture of social media and knowledge transfer, the culture of social media and work performance, also of the knowledge transfer and work performance. The research samples consisted of 300 employees in the city of Medan and the data research collection used questionnaires. Meanwhile, the data analysis technique used partial least square. The result of the study indicates that there are significant and positive relationship between the culture of social media and knowledge transfer, the culture of social media and work performance, and the knowledge transfer and work performance.