The magnetic properties of the novel compound GdCo3Sn have been investigated with susceptibility, magnetization and 119Sn Mössbauer spectroscopy measurements in the 4.2-300 K range. The sample was prepared in an arc furnace and annealed for 30 days. XRD data showed the presence of Gd2Co17 and GdCoSn in addition to the compound of interest. Magnetization curves showed ferromagnetic behavior. The Mössbauer spectra consisted of two magnetic subspectra, one corresponding to each Sn-containing compound. Magnetic ordering temperatures of both GdCo3Sn (Tc = 133 ± 2 K) and GdCoSn(TN = 27 ± 2 K) have been determined from the hyperfine field thermal dependence. The corresponding hyperfine fields at 4.2 K were 16.0 and 11.5T, respectively. The GdCo3Sn saturation moment was estimated as 6.3μB/f.u. © 2001 Elsevier Science B.V. All rights reserved.