A new series of remarkably isostructural 3d-4f compounds, [Ni3Ln(hmp)4(OAc)5]·H2O·CH2Cl2 (Ln = Gd (1), Tb (2), Dy (3), Ho (4), Y (5)) were synthesized based on a simple one-pot self-assembly method. Magnetic measurements demonstrated the ferromagnetic property of the [Ni3Ln] cores and the heterometallic influence on the magnetocaloric properties. This study suggested that robust and discrete intermetallic cubanes can be an alternative to other magnetically active materials such as high-nuclearity aggregates or clusters whose structures are not generally controlled by common synthetic methodological designs.