The investigation of the structural, electronic, optical and thermoelectric properties of Ag3XY2 (X = Cu, Cd, Zn; YSe, Te) with full potential linearized augmented plane wave (FP-LAPW) method has been carried. To get accurate bandgap values the modified Becke-Johnson (mBJ) exchange potential was applied. Two materials Ag3CuSe2 and Ag3CuTe2 have band gap values of 0.62 eV and 0.53 eV. TDOS plot of these materials gives the contribution of each element (Ag, Cu, Se/Te) in VBM and CBM. The optical properties found that Ag3CuTe2 has higher optical conductivity than Ag3CuSe2 and also has a high absorption coefficient. Thermoelectric properties were calculated and it is observed that the numerical value of Seebeck coefficient of Ag3CuSe2 is higher than Ag3CuTe2 at room temperature. But from the calculation of the figure of merit (ZT), we concluded that Ag3CuTe2 has high value of ZT than Ag3CuSe2 in both p−type and n−type regions. So, Ag3CuTe2 can be used as the best thermoelectric material in both p−type and n−type as compared to Ag3CuSe2.