Contracting approaches have been used in various forms to improve the delivery of public health services in low- and middle-income countries. Cambodia has embarked on a public-sector reform that includes a model of internal contracting of health care through the Ministry of Health, supported by incentive payments for staff and facilities. Contracting for health care in Cambodia has evolved through three phases during 1997–2015, each with particular design features, arrangements, and structures; different levels of involvement of local and international stakeholders; and modifications based on evidence from operational research. Based on a review of published and gray literature and interviews with 29 local and international key informants, we identify national ownership, financial sustainability, and the need to strengthen service delivery institutions as the major forces that have shaped contracting in Cambodia, culminating in the move to internal contracting arrangements for public health care delivery. There remains a need to strengthen contracting governance arrangements.