Background: For constitutive modeling of foams at high strain rates, it is necessary to dynamically probe their yield surface under triaxial conditions. Objective: To demonstrate dynamic triaxial characterization of foams, using a split-Hopkinson pressure bar (SHPB), in which the yield surface can be probed in various directions in the effective versus mean stress space. Methods: A conventional SHPB is augmented with a triaxial cell, using which one can dynamically apply both axial and lateral loads. The methodology is described in detail, analyzed using a one-dimensional analytical model and demonstrated using experiments. Results: We show using analysis, and experiments on polyurethane (PU) closed-cell foams that the yield surface in the effective versus hydrostatic stress space can be probed dynamically in more than one direction by varying the cross-sectional area of the specimen used. Conclusions: A methodology is presented to probe the yield surface of foams at high strain rates using the split-Hopkinson pressure bar. It was found that the uniaxial strength of PU foams increased with the loading rates. However, there was no significant enhancement of the hydrostatic strength with respect to the loading rates. © 2023, Society for Experimental Mechanics.