The Social Determinants of Health (SDH) encompass the socioeconomic, cultural, environmental, and structural conditions that shape individual and collective well-being, transcending purely biological factors. In Brazil, deeply entrenched historical inequalities manifest starkly in divergent health indicators across distinct population groups. Recognizing these determinants is essential for designing effective policies that promote social justice and equitable health outcomes. Established by the 1988 Federal Constitution, the Brazilian Unified Health System (SUS) is guided by the principles of universality, comprehensiveness, and equity. Universality ensures everyone has access to healthcare regardless of social standing, while comprehensiveness addresses the full spectrum of health needs—from prevention to rehabilitation. Equity requires prioritizing the most vulnerable populations to reduce unjust disparities. Despite these foundational principles, the SUS continues to grapple with SDH-driven barriers such as poverty, low education, inadequate housing, and lack of sanitation. These persistent structural inequities limit access to care, particularly in the historically underdeveloped North and Northeast regions. Comprehensiveness demands a continuum of multiprofessional, intersectoral care, yet effective coordination across education, housing, sanitation, and labor sectors remains limited—even amid the expanded reach of the Family Health Strategy. Equity is further challenged by the disproportionate health burdens borne by Black and Indigenous communities and residents of peripheral urban zones. These disparities stem from historical exclusion and racial oppression, necessitating culturally sensitive, affirmative public policies. Primary SDH in Brazil include income, education, employment, housing, sanitation, urban violence, and racial/ethnic disparities. Extreme poverty exposes populations to unsanitary environments and poor nutrition, fueling a cycle of vulnerability to both infectious and chronic diseases. Education is a pivotal determinant, enabling health literacy, treatment adherence, and preventive behavior. Conversely, insufficient sanitation contributes to the spread of diarrhea and waterborne diseases. Labor conditions, marked by informality and job insecurity, compromise social protection and heighten mental and physical health risks. Urban violence exacerbates trauma, chronic stress, and mortality rates. Racial inequities—driven by institutional racism—undermine access to quality care and result in differential health outcomes for Black and Indigenous communities. Institutional initiatives like the Indigenous Health Policy and the Family Health Strategy have advanced primary care coverage for vulnerable groups. Yet challenges remain: insufficient funding, overburdened personnel, and weak intersectoral collaboration diminish their impact. Adequate and equitable SUS financing is indispensable for realizing its core principles. Social participation via health councils and conferences fosters democratic governance and responsiveness to community needs. The COVID-19 pandemic starkly revealed the nexus between SDH and health disparities—exemplified by unequal exposure, resource access, and economic fallout—underscoring the urgency for intersubjective, intersectoral action and targeted affirmative policies. In conclusion, SDH significantly shape Brazil’s health landscape. Although universality, comprehensiveness, and equity are constitutionally enshrined, their enactment is hindered by structural inequities. Advancing equitable health necessitates integrated public policies that address intersecting social determinants, strengthen SUS funding, valorize social participation, and implement affirmative measures for vulnerable populations. Only through political, social, and technical commitment can Brazil realize a truly universal, comprehensive, and equitable health system that supports social justice and collective well-being.