A new bis-phenanthroline dicopper(II) complex has been synthesized and characterized by elemental analysis and spectroscopic methods. The molecular structure of the dinuclear Cu(II) complex [Cu2(μ-CH 3COO)(μ-H2O)(μ-OH)(phen)2]2+ (phen = 1,10-phenanthroline) (1) was determined by single crystal X-ray diffraction technique. The coordination environment around each Cu(II) ion in complex 1 can be described as slightly distorted square pyramidal geometry. The distance between the Cu⋯Cu centers in the complex is found to be 2.987 Å. The electronic, redox, phosphate hydrolysis, DNA binding and DNA cleavage have been studied. The antiproliferative effect of complex 1 was confirmed by the lactate dehydrogenase (LDH) enzyme level in MCF-7 cancer cell lysate and content media. The dicopper(II) complex inhibited the LDH enzyme as well as the growth of the human breast cancer MCF7 cell line at an IC 50 value of 0.011 μg ml-1. The results strongly suggest that complex 1 is a good cancer therapeutic agent. Electrochemical studies of complex 1 showed an irreversible, followed by a quasi-reversible, one electron reduction processes between -0.20 to -0.8 V. Michaelis-Menten kinetic parameters for the hydrolysis of 4-nitrophenyl phosphate by complex 1 are kcat = 3.56 × 10-2 s-1 and KM = 4.3 × 10-2 M. Complex 1 shows good binding propensity to calf thymus DNA, with a binding constant value of 1.3 (±0.13) × 105 M-1 (s = 2.1). The size of the binding site and viscosity data suggest a DNA intercalative binding nature of the complex. Complex 1 shows efficient hydrolytic cleavage of supercoiled pBR322-DNA in the dark and in the absence of any external reagents, as demonstrated by the T4 ligase experiment. The pseudo-Michaelis-Menten kinetic parameters for DNA hydrolysis by complex 1 are kcat = 1.27 ± 0.4 h-1 and KM = 7.7 × 10-2 M. © 2011 The Royal Society of Chemistry.