Abstract The intention of the current flow model is to investigate the significance of bioconvection in stagnation point flow of third grade nanofluid containing motile microorganisms past a radiative stretching cylinder. The impacts of activation energy and stagnation point flow are also considered. In addition the behavior of thermophoresis diffusion and Brownian motion are observed. Nanofluid can be developed by dispersing the nanosized particles into the regular fluid. Nano-sized solid materials for example carbides, grephene, metal and alloyed CNT have been utilized for the preparation of nanofluid. Physically, regular fluids have low thermal proficiency. Therefore, nano-size particles can be utilized to enhance the thermal conductivity of the host fluid. Nanofluids have many features in hybrid power engine, heat transfer, and can be used in cancer therapy and medicine. The formulated system of flow problems are transformed into dimensionless coupled ordinary differential expressions system via appropriate transformation. The systems of converted governing expressions are computed numerically by employing well known bvp4c solver in MATLAB software. The outcomes of emerging physical flow parameters on the velocity profile, volumetric concentration of then nanoparticles, rescaled density of the motile microorganisms and nanofluid temperature are elaborated graphically and numerically. Furthermore, velocity of third-grade fluid intensifies for higher values of third-grade fluid parameter and mixed convection parameter while opposite behavior is detected for buoyancy ratio parameter and mixed convection parameter. Temperature distribution grows for higher estimation of temperature ratio parameter and Biot number. Higher amount of Prandtl number and Lewis number decreases the concentration of nanoparticles. Concentration of microorganisms reduces by growing the values of velocity ratio parameter and bioconvection Lewis number.