The primary goal of this research is to investigate the dynamics of nanoparticle-mediated blood flow in the presence of bioconvection effects caused by microorganisms. The boundary layer problem of unsteady magnetohydrodynamic blood flow in the porous medium of tissues in stretching motion is studied. The Casson fluid model of blood flow is mathematically represented by a system of partial differential equations (PDE). The resulting set of governing equations is numerically solved, and the physical interpretation is given for the outcomes that are presented as graphs and tables. The temperature and concentration distribution of blood, along with the organism density profile in the corresponding boundary layer, are plotted, and the effects of various physical parameters, including magnetic field, radiation, chemical reaction, and permeability of the porous medium, on the results are investigated. Additionally, physical effects on the heat and mass transfer coefficients of the flow are also discussed. It is observed that the rate of heat transfer and the temperature profile are improved by increasing the values of the thermophoresis and Brownian motion parameters. Furthermore, at the lowest value of the permeability parameter and the highest value of the Brownian motion factor, the maximum heat transfer rate is observed. The findings of the study bear the promise of significant application in targeted drug delivery, magnetic therapy, and therapeutic hyperthermia treatments.