Erbium (Er)- and Ytterbium (Yb)-codoped monoclinic {\text{KLu}\left({\text{WO}}_4\right)}_2 single crystals were grown by top seeded solution growth-slow cooling method for several different doping concentrations. Growth parameters have been optimized to obtain macrodefect-free single crystals. Er energy levels involved in the {{}^{4}I}_{13/2}\to {{}^{4}I}_{15/2} were determined by 6\text{\hspace{0.17em} K} polarized optical absorption. The maximum emission cross section for this electronic transition has been evaluated, being 2.85\times {10}^{-20}{\text{cm}}^2 for E\parallel N_{\text{m}} at 1535\text{\hspace{0.17em} nm} . Laser oscillation in the 1.5\mu \text{m} range was obtained by pumping the Yb ion at 980\text{\hspace{0.17em} nm} and sensitizing Er. The maximum output power achieved was 152\text{\hspace{0.17em} mW} , with 1.2% slope efficiency.