Over the last few decades, the boundary between public and private responsibility in old-age pension provisions has been redrawn throughout Europe. A new, public-private mix has emerged, not only in pension policy, but also in pension administration. The purpose of this article is to map and conduct a comparative analysis of the administrative design of public-private partnerships (PPPs) in European pension regimes, with a specific focus on how accountabilities are institutionally enforced within the PPP design. Previous literature has recognized accountability as an important factor in promoting trust in mandated pension schemes. However, as the literature on PPPs suggests, institutional arrangements of accountability are more complex in the case of PPPs than has been suggested by previous studies on pension administration. Thus, there is a need for further elaboration of existing comparative models. This study's analysis examines 19 old-age pension schemes that existed in 18 European countries at the beginning of 2013. The findings suggest that significant variations in accountability structures exist, even among schemes that are similar in terms of their pension policy targets. It is concluded that various schemes suffer from ineffective accountability structures that may compromise the legitimacy and sustainability of PPP-type pension schemes.