We calculate the flux and spectrum of gamma-rays emitted by a two-temperature advection-dominated accretion flow (ADAF) around a black hole. The gamma-rays are from the decay of neutral pions produced through proton-proton collisions. We discuss both thermal and power-law distributions of proton energies and show that the gamma-ray spectra in the two cases are very different. We apply the calculations to the gamma-ray source, 2EG J1746-2852, detected by EGRET from the direction of the Galactic Center. We show that the flux and spectrum of this source are consistent with emission from an ADAF around the supermassive accreting black hole Sgr A*. The model uses accretion parameters within the range made likely by other considerations, and requires a power-law energy distribution of proton s. If this model is correct, it provides evidence for the presence of a two temperature plasma in Sgr A*, and predicts gamma-ray fluxes from other accreting black holes which could be observed with more sensitive detectors.