The effects of adding Gd on the Curie temperature (T_C), glass-forming ability (GFA), and magnetocaloric effect (MCE) were studied in Fe_68-xGd_xTb₅B₂₃Nb₄ (x = 0, 2, and 6) glassy alloys prepared by suction casting. It was shown that when Gd content was exchanged with Fe partially for x = 2, GFA was increased, whereas for x = 6, adding Gd content has reduced the GFA and amorphous structure could not be obtained. Critical diameter was found to be 3 mm for Fe₆₆Gd₂Tb₅B₂₃Nb₄ bulk metallic glass (BMG). By exchanging Gd with Fe partially, T_C could effectively be tuned in a quite broad temperature interval from 487 K (x = 0) to 380 K (x = 6) for which amorphous structure could not be obtained. Maximum magnetic entropy change (−ΔS_M)^max values were found to be 1.16, 0.84 Jkg⁻¹K⁻¹, and 0.54 Jkg⁻¹K⁻¹ as well as, refrigeration capacity (RC) values were obtained as 116 J/kg, 84.84 J/kg, and 40.50 J/kg under a low field change of 2 T for x = 0, 2, and 6, respectively. Although T_C was shifted to lower temperatures by exchanging Fe with Gd partially, (−ΔS_M)^max decreased almost half of the base alloy and RC decreased approximately 1/3 of the base alloy.