Two new Schiff base copper(II) complexes, [CuL¹(tmen)] (1) and [Cu₂L₂² (tmen)] (2) {where, H₂L¹ = N-(salicylidene)-L-valine, H₂L² = N-(3,5-dichlorosalicylidene)-L-valine and tmen = N,N,N',N'- tetramethylethylene-1,2-diamine} have been synthesized and characterized by molar conductance, elemental analyses, VSM-RT, UV-Vis, FTIR, EPR, and CD spectra. Both the complexes were structurally characterized by single crystal XRD. The crystal structure of complex 1 displays a distorted square pyramidal geometry in which Schiff base is coordinated to the Cu(II) ion via ONO-donor in the axial mode, whereas, the chelating diamine displays axial and equatorial mode of binding via NN-donor atoms. The crystal structure of the complex 2 reveals a syn-anti mode of carboxylate bridged dinuclear complex, in which, the coordination geometry around Cu(1) is square pyramid and distorted square planar around Cu(2). The target complexes were screened for in vitro antidiabetic activity. Both the complexes showed good inhibitory activity for α-amylase and α-glucosidase.