Rare earth (RE) Tb(3+)-doped high quality ZnSe nanocrystals (NCs) were synthesized by a facile chemical hot-injection method. ZnSe:Tb(3+) nanocrystals exhibited broadband absorption below the first excitonic absorption peak. Photoluminescence spectra showed Tb(3+) emission lines in the visible spectral window at room temperature when excited by UV radiation below the band-edge of the host ZnSe nanocrystals. Our experimental results indicate optical down-conversion in these Tb(3+)-doped Zn-chalcogenide nanocrystals via energy migration from host ZnSe to the Tb(3+) dopant. The host-dopant energy transfer mechanism for this ZnSe:Tb(3+) nanocrystal system is correlated with the emission spectra.