While their power is declining, unions and workers remain prominent actors in society. Therefore, there is a need to bring power resource theory back to the analytical forefront in the study of contemporary labour politics and labour market sociology. It provides the analytical perspectives necessary for a comprehensive and historical understanding of labour markets and labour politics. However, this article argues that the original theory developed by Korpi needs to be reassessed and further developed. Revisiting the original theory and reviewing common criticism, the authors argue that power resource theory should pay closer attention to how different types of power resources are mobilised and used and how actors’ interests are shaped during that process. The article seeks to address these issues and thus move power resource theory forward and pave the way for future theorisation.