<p>In this study, large eddy simulations of natural convection in a cubical cavity with differently heated walls were conducted to investigate the anisotropic characteristics of turbulent flows with respect to spanwise boundary conditions at Rayleigh (<i>Ra</i>) number range of 10⁵ to 10⁸. The adiabatic and cyclic conditions were imposed on the spanwise boundaries, respectively. The flow in the cubical cavity was steady at a very low <i>Ra</i> number of 10⁵ regardless of spanwise boundary conditions. Whereas one- and two-component turbulences were dominant at <i>Ra</i> = 10⁶, and the distribution of the turbulence state differed significantly depending on the spanwise boundary conditions. As <i>Ra</i> increased to 10⁷ and further to 10⁸, the adiabatic boundary condition made the turbulent flows adjacent to the spanwise boundaries resemble the two-component state while the flow state was close to the three-component state when using the cyclic boundary condition.</p>