In the WHO Western Pacific Region, traditional medicine has extensively been used by communities as part of primary health care which is critical foundation for achieving universal health coverage (UHC). This paper conceptualizes integration of traditional and complementary medicine (T&CM) into national health systems and explores how such integration can contribute to pathways toward UHC. Integration has been variously conceptualized at health system, service delivery, and consumer levels. Integration can be conceptualized based on the level of institutionalization of T&CM in national health systems (i.e. regulation of T&CM, education system, monitoring and health financial scheme). According to it, countries and areas of the Region can be categorized: countries with: ‘well-established integration strategies’; ‘in-process of developing and implementing integration policies’; ‘mixed-level of integration’; or ‘indigenous traditional medicine practiced outside the national healthcare system’. Integration of T&CM may offer pathways to advance five health system attributes essential to achieve UHC, namely: quality; efficiency; equity; accountability; and sustainability and resilience. It can contribute to improving quality of healthcare services through regulation of T&CM products, practitioners and services used by communities; meeting population needs in ageing population and managing non-communicable diseases; improving equitable access to care through health insurance coverage of T&CM; improving accountability by monitoring and use of data for informed-policy decisions on T&CM; and strengthening sustainability and resilience through maximizing potentials of T&CM in managing outbreaks of infectious diseases and disasters. Depending on the level of integration, actions to move forward integration of T&CM as a pathway toward UHC will be various.