This is a Pd-H-He embedded-atom method potential developed to enable modeling of He bubbles formed by the radioactive decay of tritium in Pd. It incorporates helium into an existing Pd-H potential while addressing two challenging paradoxes: (a) Interstitial He atoms can dramatically lower their energies by forming dimers and larger clusters in Pd but are only bound by weak van der Waals forces in the gas phase. (b) He atoms diffuse readily in Pd yet significantly distort the Pd lattice with large volume expansions.