Many countries are adopting essential packages of health services (EPHS) to implement universal health coverage (UHC), which are mostly financed and delivered by the public sector, while the potential role of the private health sector (PHS) remains untapped. Currently, many low-income and lower middle-income countries (LLMICs) have devised EPHS; however, guidance on translating these packages into quality, accessible and affordable services is limited. This paper explores the role of PHS in achieving UHC, identifies key concerns and presents the experience of the Diseases Control Priorities 3 Country Translation project in Afghanistan, Ethiopia, Pakistan, Somalia, Sudan and Zanzibar. There are key challenges to engagement of the PHS, which include the complexity and heterogeneity of private providers, their operation in isolation of the health system, limitations of population coverage and equity when left to PHS's own choices, and higher overall cost of care for privately delivered services. Irrespective of the strategies employed to involve the PHS in delivering EPHS, it is necessary to identify private providers in terms of their characteristics and contribution, and their response to regulatory tools and incentives. Strategies for regulating private providers include better statutory control to prevent unlicensed practice, self-regulation by professional bodies to maintain standards of practice and accreditation of large private hospitals and chains. Potentially, purchasing delivery of essential services by engaging private providers can be an effective 'regulatory approach' to modify provider behaviour. Despite existing experience, more research is needed to better explore and operationalise the role of PHS in implementing EPHS in LLMICs.