The coverage‐ and structure‐dependent empty electronic states of Sb multilayers on nearly unrelaxed GaAs(110) and relaxed InP(110) have been investigated using inverse photoemission (IPES) and low energy electron diffraction. Two significant Sb‐derived empty states, termed features A and B, are used to characterize the evolution of ordered, metastable Sb multilayers and the ordered first monolayer. Feature A appears ∼0.30 and ∼0.35 eV aboveEFfor ordered metastable Sb multilayers onp‐GaAs(110) andp‐InP(110), respectively, while feature B appears at 2.0 eV for 1 ML of ordered Sb. Feature A resonates for photon energies of IPES near ℏωp=15.9 eV because radiative decay of a plasmon within the Sb film provides a decay channel that competes with the inverse photoemission channel. This resonance occurs for thicknesses greater than ∼3.5 ML for GaAs(110) and ∼2 ML for InP(110) for overlayers annealed at 475 K following Sb growth at 300 K. Structural studies reveal that the resonance features of IPES are correlated with metastable structures of the Sb layers. Very gradual relief of strained‐layer structures, coherent with (110) surfaces, may contribute to the existence of metastable phases for coverages below ∼10 ML. For Sb/GaAs(110), the metastable structures consist of long‐range‐ordered (110) domains with Sb crystallites between them. For Sb/InP(110), the metastable structures may be associated with a fairly continuous, periodic distribution of atomically corrugated (110) domains along [001], and the plane defined by the Sb zig–zag chains is not parallel to the unrelaxed (110) surface. These metastable structures may provide various coupling conditions for the momenta of the photon and the electron‐excited Sb plasmons.