Background and objectives: Low socioeconomic status (SES) is consistently associated with chronic stress, poor health, and premature death in high income countries (HICs). However, the degree to which SES gradients in health are universal, or even steeper under contemporary, post-industrial conditions, remains poorly understood. Methodology: We quantified material wealth and several health outcomes among a population of traditional pastoralists, the Turkana of northwest Kenya, who are currently transitioning toward a more urban, market-integrated lifestyle. We assessed whether SES associations with health differed in subsistence-level versus urban contexts. We also explored the causes and consequences of SES-health associations by measuring serum cortisol, potential sociobehavioral mediators in early life and adulthood, and adult reproductive success (number of surviving offspring). Results: High SES predicts better self-reported health and more offspring in traditional pastoralist Turkana, but worse cardiometabolic health and fewer offspring in urban Turkana. We do not find robust evidence for either direct biological mediators (i.e., cortisol) or indirect sociobehavioral mediators (e.g., adult diet or health behaviors, early life experiences) of SES-health relationships in either context. Conclusions and implications: While social gradients in health are common in non-human primates, small-scale human societies, and HICs, we find that relationships between wealth and health can vary dramatically within a single population. Our findings emphasize that under different economic and societal circumstances, social status effects on health may manifest in very different ways.