Metallocene-based polyolefin (MPO) foams possess a closed-cell structure which is in contrast to the open-celled structure of polyurethane (PU) foams. In this study, we investigate the effects of gamma-irradiation on the mechanical behavior of MPO foams using PU foam behavior as a basis. Compressive step-strain experiments reveal a two-step relaxation process in MPO foams, dominated by polymer chain relaxation at short times and gas diffusion from the closed cells at longer times. On the other hand, the relaxation in PU foams is similar to fully crosslinked polymers with the relaxation modulus reaching an equilibrium value after an initial decay. The closed-celled structure of MPO foams lends to rapid stress relaxation and low structural recoverability upon application of compressive loads. Exposure to gamma radiation induces crosslinking in MPO foams and improves their resilience and recoverability. Stress relaxation tests reveal that nonradiated MPO foams show complete relaxation and structural loss at high temperatures. In contrast, radiated MPO foams show a significant retardation in relaxation kinetics and structural stability attributed to radiation-induced crosslinking. Dynamic rheology and solvent-extraction studies also support the results obtained from stress-relaxation experiments.