The effect of stress on pore closure was studied by hot isostatic pressing and hot forging of sintered Al2O3, cubic ZrO2, and finer‐grained Al2O3/ZrO2(cubic) composite materials containing pores remnant of monosized plastic spheres. For the temperature‐time conditions explored, plastic deformation was the dominant mechanism for pore shape change and closure. Namely, only pores in the highly deformable two‐phase material were observed to either change shape (under uniaxial forging) or shrink (during hot isostatic pressing). Large plastic strains (0.3 to 0.6, dependent on location) were required to produce pore closure under forging conditions. At temperatures where the two‐phase materials were sufficiently deformable to affect pore closure, pores close to the surface would puncture as the thin web of material separating the pore from the surface was deformed into the pore. These results are discussed in terms of the common practice of finishing by hot isostatic pressing of sintered ma