Strengthening health systems is a key challenge to improving the delivery of cost-effective interventions in primary health care and achieving the vision of the Alma-Ata Declaration. Effective governance, financial and delivery arrangements within health systems, and effective implementation strategies are needed urgently in low-income and middle-income countries. This overview summarises the evidence from systematic reviews of health systems arrangements and implementation strategies, with a particular focus on evidence relevant to primary health care in such settings. Although evidence is sparse, there are several promising health systems arrangements and implementation strategies for strengthening primary health care. However, their introduction must be accompanied by rigorous evaluations. The evidence base needs urgently to be strengthened, synthesised, and taken into account in policy and practice, particularly for the benefit of those who have been excluded from the health care advances of recent decades.