This study reports the synthesis, structural characterization, optical and electrical properties of (Cu2-xAgx)ZnSnSe4 solid solutions. Powder X-ray diffraction patterns and Rietveld refinement results were consistent with phases belonging to the I4¯2m space group (stannite-type). The Raman spectra peaks were fitted, displaying the main A2 vibrational mode at about ~ 187 cm−1. FWHM and intensity of the Raman peaks reflect the high crystallinity. Cu1.90Ag0.10ZnSnSe4 and Cu1.80Ag0.20ZnSnSe4 exhibit typical semiconductor p-type behavior with a carrier concentration of ~ + 1019 cm−3. The optical band gaps calculated based on the UV–Vis-NIR spectra were Eg ~ 0.6–0.8 eV.