<p>Ternary hybrid nanofluids are obtaining prominence for their potential to considerably enhance heat transfer in several applications. This study is a comprehensive numerical investigation into the heat transfer dynamics and entropy generation of a micropolar blood-based ternary hybrid nanofluid flowing over a vertical stretching cylinder, under the effects of Joule heating, buoyancy, viscous dissipation, uniform heat source, and thermal radiation (linear, non-linear, and quadratic). The flow structure is relevant to physiological circumstances such as blood flow around malignant tumor cells, where nanoparticles can facilitate targeted drug delivery and improve radiation therapy results. Mathematical modeling results in coupled nonlinear governing equations which are solved using a fourth-order Runge–Kutta method with shooting technique, ensuring robust computational accuracy. The results reveal that Joule heating significantly enhances fluid temperature but diminishes flow velocity, while non-linear thermal radiation yields the most pronounced improvement in heat transfer rate compared to other radiation models. Entropy generation analysis identifies viscous dissipation and buoyancy as the primary contributors to entropy production. Additionally, an artificial neural network (ANN) model was trained using the numerical data, which demonstrates high predictive accuracy for heat transfer rates. These findings elevate the understanding of blood transport phenomena over stretched surfaces and offer novel insights for targeted drug delivery and optimization in radiation therapy applications. This work aims to highlight the biomedical relevance of ternary hybrid nanofluids in complex physiological and therapeutic contexts.</p>