The present study aims at discussing the onset of convection and heat transfer rate in a Casson nanofluid saturated in anisotropic porous enclosures of three types: shallow, square, and tall. The effects of Brownian motion and thermophoresis are included in the model. Normal modes are used to obtain the expression of stationary thermal Rayleigh number. Further, nonlinear stability analysis is performed using the truncated Fourier series expansion. The Nusselt number is calculated from the Lorentz model. The effects of pertinent flow governing parameters such as Casson parameter, thermal anisotropic parameter, mechanical anisotropic parameter, and nanoparticle concentration Rayleigh number are shown graphically on the onset of convection, Nusselt number, streamlines, isotherms, and isohalines. It is observed that shallow enclosure allows quick heat transfer by setting the convection earlier. Furthermore, it is concluded that the use of Casson-based single-walled carbon nanotube suspension (SWCNTS) enhances heat transportation and strengthens the magnitude of streamlines.