AbstractThe theoretical investigation of thermal convection in a horizontal layer of micropolar nanofluid is examined within the rule of linear stability hypothesis. The model applied for nanofluid integrates the impact of Brownian and thermophoresis diffusions. The flux of the volumetric fraction of nanoparticles is considered to be nil on the boundaries. The critical eigenvalues are achieved using the Galerkin approach, and the results are discussed and illustrated graphically. The results show that the Lewis number, the modified diffusivity ratio, the nanoparticle Rayleigh number, and the coefficient of coupling amid spin and heat flux accelerate the onset of convective motion, whereas the micropolar parameter and the coefficient of coupling amid vorticity and spin delay the onset of convective motion in the system.