The magnetic properties of Mn1-xTMxAlGe (TM = V, Fe and Cu) were investigated for x ≤ 0.2. The spontaneous magnetization decreased with increasing x. A remarkable decrease in the Curie temperature TC was observed for TM = Fe. For ferromagnetic MnAlGe (x = 0) and TM = nonmagnetic Cu (x = 0.2), Curie-Weiss law was confirmed. The compounds with TM = V and Fe (x = 0.2) did not show Curie-Weiss law, and the data of reciprocal susceptibility vs. temperature bent, indicating change of the magnetism from ferromagnetism. Obtained results suggested that the magnetic moments of V and Fe were aligned antiparallel to those of Mn, resulting in the ferrimagnetism-like behavior.