A keystone of primary healthcare is the interprofessional team-based approach in which different health and social care professionals work together through interdisciplinary collaboration and deliver services to assist clients, families and communities in health-related decision-making. Studies in different countries have proven that social workers play a significant role in primary healthcare, particularly with regard to mental health issues. Integrating social work into primary healthcare settings can address psychosocial needs through a holistic team approach. However, the integration of social work into primary healthcare and interdisciplinary collaboration can be problematic. The barriers to such collaboration may include differences in power and culture between social workers and healthcare professionals, lack of role clarity and trust, inadequate interprofessional education and training, insecurity relating to professional identity, disregard of other professions, poor communication, organisational barriers and so on. In Hong Kong, primary healthcare reform emphasises the integration of primary healthcare and social services through medical-social collaboration in the community. Traditionally, social workers in Hong Kong play a minor role in primary healthcare teams. Integrating social work and social services into primary healthcare systems and promoting medical-social collaboration has become an important topic for deliberation. In this chapter, the potential roles of social workers in primary healthcare, and the challenges of integrating social workers into primary healthcare teams through medical-social collaboration will be discussed.