Squatting has been present in Central and Eastern Europe since the fall of state socialism and Poland is pointed out as exceptional in the development of squatting in the area. However, looking closer at the squatting environment in Warsaw reveals that the movements’ successes are a result of a cross-movement alliance with the tenants’ movement. The cooperation between squatters and tenants have in a short period of time gained a strong negotiating position vis-à-vis local authorities in Warsaw. The objective of this article is to analyse the mechanisms behind the cooperation of squatters’ and the tenants’ movements and in particular the cognitive processes behind the formation of an alliance. Specific research questions posed in the article cover how the cooperation between the squatting movement and the tenants’ movement emerge in the city, and what cognitive processes characterize the cooperation. The empirical material for the study consists of altogether 40 semi-structured interviews with squatters and activists in the tenants’ movement in the city. It is argued in the article that the development of alliance formation includes processes of defining common goals, underplaying of differences, and recognizing common strength. Moreover, in order to reach the point when the alliance is formed the process of recognition of common strength needs to be successful in both movements resulting in a shared perception of empowerment.