To improve access to affordable primary health care and preventive services, in 2019 Rwanda's Ministry of Health inaugurated eight laboratory-equipped second-generation health posts (SGHPs) in the Bugesera District. Patient fees through Rwanda's insurance system (mutuelles) funded most operational costs through a public-private partnership. This prospective, controlled trial evaluated the posts' impact and cost-effectiveness. Our evaluation matched the rural cells containing these posts to eight control cells in Bugesera without formal health posts. We assessed costs using 2 years of financial data; accessed use statistics at SGHPs, health centers, and in the international literature; interviewed 1,952 randomly selected residents; conducted eight focus groups; and performed difference-in-differences regressions and survival analyses. Second-generation health posts increased primary care use by 1.83 outpatient visits per person per year (P < 0.0001). Of the 10 prevention indicators compared with trends, two improved significantly with SGHPs (two showed nonsignificant improvements), and one indicator experienced a significant deterioration. Second-generation health posts generated health improvements at a low cost and achieved a small, but favorable, 5% margin of revenues over financial costs. Second-generation health posts produced a very favorable incremental cost-effectiveness ratio of only $101 per disability-adjusted life year averted-only 13% of Rwanda's per-capita gross national income. In conclusion, SGHPs improved substantially the quantity of affordable outpatient care per person. However, net impacts on quality and completeness of care and prevention, although favorable, were small. For further improvements in access and quality of care, Rwanda's health authorities may wish to incentivize quality and strengthen coordination with other health system components.