We grew good-optical-quality KYb~WO4)2 single crystals doped with erbium ions by the top seeded solution growth slow cooling method. Optical absorption of erbium was performed at room temperature ~RT! and at 6 K. Green photoluminescence of erbium was achieved at RT and 6 K after selective excitation of ytterbium ions at 940 nm (10 638 cm21). The splitting of all found excited energy levels and the ground energy level of erbium in KYb~WO4)2 is presented derived from the accurate absorption and emission measurements, respectively. The lifetime of the Stokes and the anti-Stokes green emissions of erbium were measured after excitation at 488 nm (20 490 cm21) and 940 nm(10 638 cm21), respectively. We propose applying the up-conversion model to the observed green emission.