Magnetization and crystallographic measurements are reported for the Heusler alloy series (NixCu1−x)2MnSn. With the exception of Cu2MnSn and perhaps (Ni0.1Cu0.9)2MnSn all of the samples prepared had the cubic Heusler L21 structure at room temperature. The lattice parameter varies linearly as a function of composition. The saturation moment is constant at approximately 4μβ per manganese atom throughout the series. Curie temperatures vary smoothly but non-linearly with composition, providing some evidence for at least two competing mechanisms in the determination of the Curie temperature.