A three-dimensional (3D) image rendering method and an apparatus are provided. The 3D image rendering method includes determining intersection points between candidate rays and an optical layer based on a first refractive index of a first medium that is disposed between a display panel and the optical layer and a second refractive index of a second medium that is outside a 3D display apparatus, and assigning a pixel value to a pixel of the display panel based on respective distances between the intersection points and optical elements of the optical layer.