Magnetic properties of two spinel oxides solid solutions, Cu 1+x Mn 2−x O 4 and Ni 1+x Mn 2−x O 4 , are reported. These series are characterized by two magnetic transitions: the upper one, of ferrimagnetic type, occurs at about 85K (for copper-based) and at 105–110K (for nickel-based spinels), independently of the x-content; the lower transition may be related to a Néel-type collinear ordering and takes place at 30 and 45K, respectively. Application of moderate fields (H>250Oe) make both transitions to merge into one broad maximum in the magnetization, which takes place at lower temperature when applying larger fields. Magnetization cycles with temperature (ZFC/FC) or field (loops) allowed us to well characterize the ordered state. The effective moment follows the expected behavior when manganese ions are being substituted by ions of lower magnetic moment (Ni 2+ and Cu 2+ ).