Mixed metal complexes with Cu(I) and tetrathiomolybdate have been synthesized with Schiff bases of diethylenetriamine (dien) formed from benzaldehyde, salicylaldehyde, acetophenone and acetyl acetone. The complexes are characterized by elemental and thermal analysis, IR, UV-Visible spectral studies and magnetic studies. The complexes contain tetrahedral Cu(I) and Mo(VI) as tetrathiomolybdate. The complexes have the general composition [(dien-4H) (CRR’)2 (Cu2MoS4)]. xH2O, for benzaldehyde, salicylaldehyde and acetophenone complexes. where (dien-4H) stands for dien less four hydrogen atoms. However with acetyl acetone the complex, the following complex, [(dien-4H)2 (CH3CCH2CCH3)2 (Cu2MoS4)]. 12 H2O is reported.