This study reports the fabrication of Nd:YAG (i.e., Neodymium-doped Yttrium Aluminum Garnet: Y3-xNdxAl5O12) transparent ceramics of a large size by the pressure slip-casting forming technique. Colloidal suspensions of primary oxides (i.e., Y2O3, Al2O3, Nd2O3, and SiO2 used as sintering aid) were cast under pressure through a porous membrane. Cakes with a good microstructural homogeneity and mean pore diameter of 90 nm were obtained. Modeling of the pressure slip-casting process at the millimetric to centimetric scale based on a computational fluid dynamics simulation showed good agreement with experimental results in terms of the casting kinetics (i.e., cake thickness and fluid flow as a function of time) and cake permeability. As a result, it was possible to better manage pressure casting parameters in order to obtain large size and homogeneous green parts. Finally, transparent Nd:YAG ceramics sintered by vacuum sintering, followed by post-sintering treatment by Hot Isostatic Pressing (HIP), demonstrated laser slope efficiency (51.7%) and optical-to-optical efficiency (44%) with 130 mJ of output laser energy at 1064 nm equivalent to commercial single crystals.