This study investigates the Finnish government members’ argumentation prior to Finland’s strikingly unanimous parliamentary vote in favour of NATO membership on May 17, 2022. By focusing on the government representatives’ accounts, the study aims to shed light on how the NATO membership decision is crafted to represent Finland’s security interest after a decades-long tradition of military non-alignment as a cornerstone of the country’s securityand foreign policy. With help of Merlijn van Hulst and Dvora Yanow’s dynamic approach to framing based on the theoretical concept of frames as actors’ “definitions of the situation”, the study shows comprehensively the processes at play when the government members constructa NATO membership as Finland’s security interest. Furthermore, the approach reveals patterns among the representatives of how the different framings are embraced. For example, the study shows that the representatives’ framings are the most united when it comes to the view of Russia’s invasion of Ukraine as a violation of the rule-based order and the view of a NATO membership as a deterrent preventing future military attacks rather than as a solution to any immediate threat. While the dynamic approach to framing shows comprehensively the work framing does in constructing a NATO membership as Finland’s security interest, the approach has some shortcomings that future research should deal with to increase the potential of the approach in War Studies research.