Disclosed is expandable modified resin beads (1), comprising a modified resin as a base resin in which a dispersion phase (3) containing a styrene resin as a major component is dispersed in a continuous phase (2) containing an olefin resin as a major component, and a physical blowing agent. Further disclosed are expanded modified resin beads obtained by expanding the expandable modified resin beads (1), and a foamed molded article formed from the expanded modified resin beads obtained by molding the expanded modified resin beads in a mold. A volume average diameter of the dispersion phase (3) dispersed in the continuous phase (2) is 0.55 μm or more. The expandable modified resin beads (1) have, as a base resin, the modified resin contains 80 to 50 parts by mass of the styrene resin with respect to 20 to 50 parts by mass parts of the olefin resins.