Abstract Spin pumping from a metallic ferromagnet (FM) into an insulating antiferromagnet has been studied across the magnetic phase transition by means of temperature-dependent, broad-band ferromagnetic resonance (FMR) experiments. A set of spin pumping heterostructures consisting of Permalloy (Ni 80 Fe 20 ) as FM and Zn 1 − x Co x O with x = 0.3 , 0.5 and 0.6 (Co:ZnO) as partially compensated antiferromagnetic insulator has been used for which previous experiments have already pointed out the possibility of the existence of spin-pumping. The present experiments allow to reliably separate the various contributions of the temperature-dependent Gilbert damping parameter to the FMR line-width. A careful analysis of the obtained data demonstrates a significant increase of the temperature-dependence of the Gilbert damping parameter α ( T ) around the magnetic phase transition of Co:ZnO which extends up to room temperature, confirming spin pumping into the fluctuating spin sink of an antiferromagnetic/paramagnetic insulator.