In this essay Sweden’s relationship with NATO is explored in a theory consuming case study. The aim is to explain why Sweden is not a member of NATO but still wants to have a close cooperation and has entered a memorandum of understanding on Host Nation Support with NATO. The reason for not entering NATO is that Sweden wants to be military non- aligned. The memorandum of understanding on Host Nation Support is motivated by that Sweden wants to be interoperable with NATO in order to be able to give and receive military support. Other reasons are that it is a way for the Swedish military to develop, it increases efficiency and it makes Sweden more competitive by decreasing administrative costs. The reasons for Sweden’s decisions are analyzed and explained with two theories: realism and liberalism. Realism can explain well why Sweden does not want to enter a membership and liberalism can explain well why Sweden has entered the memorandum of understanding on Host Nation Support.