Microorganism cells movement in the fluid is universal and affects many ecological and biological processes, including infection, reproduction, and marine life ecosystem. There are many biological and medical applications that require an understanding of the transport process in nanofluids containing a suspension of microorganism. The present problem deals with the bioconvection of Casson nanofluid containing a suspension of motile gyrotactic microorganisms over an inclined stretching sheet in the presence of thermal radiation, viscous dissipation, and chemical reaction and magnetic field. At the surface, the influence of the thermosolutal Marangoni convection and suction/injection impact are considered. The governing equations are solved numerically by using fourth-order Runge–Kutta–Fehlberg method with shooting technique. The impact of the major pertinent parameters on the velocity, temperature, nanoparticles concentration, and density of the motile microorganism is illustrated graphically. Finally, the correlations of various crucial parameters on skin friction, local Nusselt number, Sherwood number, and local motile microorganism density number are displayed through the graphs and tables.