There is a dearth of phenomenological interpretive studies in public-private partnership (PPP) policy in education service delivery. The limited extant literature on PPPs in education hardly explores insights into how stakeholders understand them, and what they perceive as critical success factors (CSFs) for their implementation in the context of developing countries. The overarching purpose of this study is to explore the stakeholders' perceptions of PPP policy in universal secondary education (USE) and its CSFs in Uganda. It employed the interpretive paradigm and the participants were purposively selected from government bodies, partnership private schools and local communities. Document review and interviews were used as the data collection methods while the resultant data were analyzed using content and thematic techniques. The findings reveal that most stakeholders' understandings of the PPP in USE were diverse and context-specific; and that most school-based stakeholders implemented this policy without clearly understanding its origin, goals and guidelines. While most government-based stakeholders perceived the policy as successful, the majority of school-based stakeholders deemed it unsuccessful. The majority of stakeholders perceived regular policy reviews, commitment to partnership roles, sufficient funding, the selection of partners with adequate capacity, effective policy communication, regular policy monitoring and strong enforcement mechanisms as its CSFs. In view of the findings, it can be inferred that unless appropriate policy reforms and best practices informed by these findings are undertaken, the success and sustainability of PPP policy in USE would remain uncertain.