Health systems strengthening (HSS) is being increasingly recognized as a strategic cross-cutting issue in all World Health Organization (WHO) work. Health systems comprise six building blocks: service delivery; medical products, vaccines and technologies; health workforce; health systems financing; health information system; and leadership and governance. Public-private mix (PPM) approaches or partnerships consist of initiatives aimed at increasing collaboration and improving the relationships between public-public, public-private and private-private health providers. An important component of PPM is the clear distribution of tasks between the different providers involved in the provision of health care. In practice, most PPM initiatives are disease-specific and are often related to the health service delivery block mentioned above. Although there is widespread consensus that PPM initiatives are typically of an HSS nature, efforts to make explicit the links between PPM and health systems building blocks are rather uncommon. The present paper aims to identify - in order to facilitate operationalization - potential aspects linking PPM to health systems building blocks, using a few experiences from tuberculosis control and beyond. The paper targets policymakers, donors and health systems scientists and ends with a call for more aware and innovative leadership, for increased support of PPM initiatives covering various building blocks, and for more operational research.