Understood as a benefit derived from social security, healthcare provision was historically developed in Mexico within the context of labor laws and tied to the multiple social security institutions (SSIs) created throughout the first half of the twentieth century. However, the combination of an increase in informal unemployment, lack of institutional fiscal frameworks to support revenue raising, and political-economic aspects led to the development of a three-tiered system with financing and healthcare delivery practically independent from each other: 1) public health services provided by the various social-security institutions to the SSI-affiliated population, 2) public Ministry of Health (MoH) delivery for the population without affiliation to SSIs (non-SSI population) and 3) an increasingly growing private sector that complements the public health system's inability to meet population needs. During the past three decades, Mexico adopted multiple health reforms targeting the non-SSI tier with the aim of reducing inequities that result from financial and healthcare delivery fragmentation across the two tiers of the public healthcare system. These reforms included changes to health financing, workforce and shifted the fiscal attributions between states and the central government. While there exists abundant evidence on the consequences of these reforms on health system performance of the public non-SSI tier, two issues remain unexplored. First, the variation of these effects across the 32 Mexican states. Second, the absence of studies in the private sector even when almost half of national total health spending is financed through private funds. In this context, this dissertation aims to assess the participation of the private sector in health financing and workforce for the non-SSI tier of the Mexican healthcare system. To do so, it carries out three empirical studies with different research designs and data sources. The first study uses a cross-sectional design and data from an individual-level survey of adults from four Latin American countries in 2014; Mexico, El Salvador, Colombia and Brazil to investigate the association between private insurance and financial protection. Results point out that countries that managed to integrate the social security and non-social security health tiers through changes in health financing arrangements, -Brazil and Colombia- are potentially better able to provide financial protection to their population than Mexico and El Salvador, which continue to face steeper integration challenges underpinned by their health financing arrangements. The second and third studies are sub-national analyses of the effect of public health spending for the non-SSI population on financial protection (study 2) and workforce (study 3). Study 2 uses a cross-sectional design (2018) to test if states that allocate a higher level of financial resources to health for the non-SSI population are better able to protect their population against financial burden. Overall, results point to an inverse relationship between public health spending and financial protection and that this is even more pronounced in states that allocate a higher share from their own revenues. Study 3 uses multiple available data sources to build 17-year panel (2004-2020) to investigate the effect of public health spending for the non-SSI on changes in the number of physicians working in public and private settings. Results show that the rate of nurses grew more than physicians during the period of study, particularly among those working in public settings. While public health spending on the non-SSI population contributed to increased public and private workforce, there are steep variations across states. This dissertation contributes to the discussion of central government-state relations as well as the interaction between public-private sectors in healthcare, since they can no longer be independently understood.