The magnetic hyperfine fields,Bhf, for impurity119Sn atoms in Z sites of ferromagnetic Heusler alloys Co2MnZ (Z=Si, Ge) are measured by the Mössbauer effect. At 77 KBhf=−1.43±0.04 T in Co2MnSi andBhf=+1.05±0.05 T in Co2MnGe. From the comparison between the values ofBhf for Sn atoms in Co2MnZ (Z=Si, Ge, Sn), it follows that the negative contribution toBhf drops as the interatomic distance begins to increase. This radial dependence also manifests itself in the anomalies of the temperature dependences of the hyperfine fields. The temperature anomaly is positive for Sn in Co2MnGe and negative for Sn in Co2MnSi.