A new mixed metal borate, CdTbGaB2O7, was successfully synthesized using the high-temperature solution method and its crystal structure was determined by single-crystal X-ray diffraction with the following unit-cell data:P4̄21m,a=b= 7.3487(1) Å,c= 4.7247(1) Å,V= 255.150(9) Å3, andZ= 2. It belongs to a new member of the melilite family, which features a 3D framework consisting of alternately stacked [Ga(B2O7)]n5n−tetrahedral layers and (Cd2+/Tb3+) cationic layers that are interconnectedviaB(Ga)–O–(Cd/Tb) bridges. In addition, the solid solutions of CdTb1−xSmxGaB2O7(0 ≤x≤ 0.2) were preparedviathe solid-state reaction method. The combined techniques of XRD, SEM, IR/Raman, XPS and PLE/PL were employed to characterize the products. It was found that the CdTb1−xSmxGaB2O7phosphors simultaneously showed green emission of Tb3+at 545 nm and orange emission of Sm3+at 603 nm under excitation at 370 nm. The emission color can be adjusted from green to orange-red by varying the Sm3+doped contentviaan energy transfer mechanism. For CdTb0.995Sm0.005GaB2O7, a QY of 13.22% was obtained, and its emission intensity at 423 K was 94% of that at 303 K. These results show that the prepared materials can act as potential color-tunable phosphors for UV w-LEDs.