We show that Compton scattering of 511 keV electron‐positron annililation radiation produces a line‐like reflection feature at ∼170 keV from backscattered photons. Assuming a simple model of an accretion disk around a compact source, we explore the spectrum of Compton scattered annihilation line emission for a range of disk geometries, opacities, and observing angles, and we find that the line‐like feature is produced under a wide variety of conditions. We further show that such Compton backscattering of slightly redshifted annihilation line emission from the inner edge of an accretion disk could account for the 170 keV line emission and higher energy continuum observed1–3together with the 511 keV annihilation radiation from the direction of the Galactic center. Identification of the observed 170 keV line as an annihilation line reflection feature provides direct new evidence for the existence of an accreting stellar‐mass black‐hole source of annihilation radiation at or near the Galactic center.