Relationship management in IT Outsourcing (ITO) is widely accepted as a prerequisite for a successful ITO. However, there is still a need for understanding the important factors that contribute to a successful ITO relationship in large companies in Sweden. Therefore, this study wants to address this knowledge gap. The studied companies are the largest ones regarding turnover in Sweden and are present in the “Large Cap” segment at Nasdaq Stockholm Exchange. The results of this research are compared with a previous study done in 2012 in large companies in Sweden. The findings show that the most important factors (from a buyer’s perspective) for a successful ITO relationship are communication; conflict and conflict resolution; trust; commitment; cooperation; and internal competence. The identified relational factors in this study contribute to ITO research and can help ITO decision-makers in large companies to have successful ITO relationships and improve their ITO.