The Czech Republic, Slovakia, and Poland, with their shared political histories, have confronted the compounded challenges of the COVID-19 pandemic and the Ukraine war. These difficulties spurred the emergence of public-nonprofit collaboration in all three countries, each taking distinct paths. Our study aims to unravel these divergent trajectories of public-nonprofit collaboration through the lens of historical institutionalism. Using this lens, we attribute this divergence to the influence of the broader institutional environment, whose evolution has followed distinct trajectories in the examined countries. To achieve our objectives, we employed single-country case study methods, leveraging desk research and structured interviews with management informants from nonprofit organizations in the Czech Republic, Slovakia, and Poland (37 respondents in total). Our study demonstrates that the perceptions of the institutional environment by nonprofit actors directly shape the effectiveness of collaborations between the public sector and nonprofit organizations. Contrary to Western expectations, our findingsmchallenge the seemingly prevailing optimism regarding the outcomes of public-nonprofit collaboration and emphasize the influence of factors such as path dependency, mutual distrust, and prior negative experiences.