Recent studies have pointed to the substantial role of private health sector delivery of maternal and newborn health (MNH) care in low-/middle-income countries (LMICs). While this role has been partly documented, an evidence synthesis is missing. To analyse opportunities and challenges of private sector delivery of MNH care as they pertain to the new World Health Organization (WHO) strategy on engaging the private health service delivery sector through governance in mixed health systems, a more granular understanding of the private health sector’s role and extent in MNH delivery is imperative. We developed a scoping review protocol to map and conceptualise interventions that were explicitly designed and implemented by formal private health sector providers to deliver MNH care in mixed health systems.