Effective primary healthcare for children and adolescents is crucial for promoting optimal health, well-being, and development during these critical life stages. The primary healthcare system in Hong Kong adopts a unique mixed public–private model. The government is the key fund and service provider, and the private sector plays an efficient complementary role. They jointly provide effective, comprehensive, multidisciplinary, and cross-sectoral healthcare services for children and adolescents. They provide preventive and promotive services, early diagnosis, and management of common physical and mental conditions. The system is very effective, and Hong Kong has attained very low infant mortality and high vaccine coverage for vaccines recommended by the Department of Health. However, new challenges arise, due to recent increases in parental expectations, increased mental health demands, shortage of funding and manpower, unequal distribution of services, emergence of new technology and changes in the social structure. Various measures including increasing funding and manpower, redistribution and service integration, introducing new technologies, adopting community-based family-centred models, establishing a child commissioner and formulating a child health policy are discussed.