Abstract Magnetic susceptibility χ measurements in the range from 2 to 300 K were carried out on samples of the Cu 2 FeSnSe 4 and Cu 2 MnSnSe 4 compounds. It was found that Cu 2 FeSnSe 4 was antiferromagnetic showing ideal Curie–Weiss behavior with a Neel temperature T N of about 19 K and Curie–Weiss temperature θ =−200 K, while for Cu 2 MnSnSe 4 the behavior was spin-glass with a freezing temperature T f of about 22 K and Curie–Weiss temperature θ =−25 K. The spin-glass order parameter q ( T ), determined from the susceptibility data, was found to be in agreement with the prediction of conventional spin-glass theory.