The magnetism and magnetocaloric effect (MCE) of rare-earth-based tungstate compounds R 3BWO9 (R = Gd, Dy, Ho) have been studied by magnetic susceptibility, isothermal magnetization, and specific heat measurements. No obvious long-range magnetic ordering can be found down to 2 K. The Curie–Weiss fitting and magnetic susceptibilities under different applied fields reveal the existence of weak short-range antiferromagnetic couplings at low temperature in these systems. The calculations of isothermal magnetization exhibit a giant MCE with the maximum changes of magnetic entropy being 54.80 J/kg⋅K at 2 K for Gd3BWO9, 28.5 J/kg⋅K at 6 K for Dy3BWO9, and 29.76 J/kg⋅K at 4 K for Ho3BWO9, respectively, under a field change of 0–7 T. Especially for Gd3BWO9, the maximum value of magnetic entropy change ( − Δ S M max ) and adiabatic temperature change ( − Δ T ad max ) are 36.75 J/kg⋅K and 5.56 K for a low field change of 0–3 T, indicating a promising application for low temperature magnetic refrigeration.