CaGd2(MoO4)(4):Er3+/Yb3+ phosphors with the doping concentrations of Er3+ and Yb3+ (x=Er3++Yb3+, Er3+=0.05, 0.1, 0.2, and Yb3+=0.2, 0.45) have been successfully synthesized by the microwave sol-gel method, and the crystal structure refinement and upconversion photoluminescence properties have been investigated. The synthesized particles, being formed after heat-treatment at 900 degrees C for 16h, showed a well-crystallized morphology. Under the excitation at 980nm, CaGd2(MoO4)(4):Er3+/Yb3+ particles exhibited strong 525 and 550-nm emission bands in the green region and a weak 655-nm emission band in the red region. The Raman spectrum of undoped CaGd2(MoO4)(4) revealed about 15 narrow lines. The strongest band observed at 903cm(-1) was assigned to the (1) symmetric stretching vibration of MoO4 tetrahedrons. The spectra of the samples doped with Er and Yb obtained under 514.5nm excitation were dominated by Er3+ luminescence preventing the recording Raman spectra of these samples. Concentration quenching of the erbium luminescence at (H11/2I15/2)-H-2-I-4 and (S3/2I15/2)-S-4-I-4 transitions in the CaGd2(MoO4)(4):Er3+/Yb3+ crystal structure was established to be approximately at the 10at.% doping level.