Department of Chemistry, Patna University, Patna-800 005, Bihar, India Manuscript received 08 February 2010, revised 27 October 2010, accepted 03 November 2010 A series of Schiff base hetero binuclear complexes of rubidium(l) and caesium(l) of the type [Ma(acac) 2en.MbL], where Ma = Cu or Ni, Mb = Rb or Cs, acac = acetyl acetone, en = ethylenediamine, L = deprotonated o-nitrophenol, 2,4-dinitrophenol, 2,4,6-trinitrophenol, 1-nitroso-2-naphthol or 8-hydroxyquinoline have been prepared by the reaction of [Ma (acac2)en] with rubidium or caesium metal salts of corresponding organic acids in 1 : 1 molar ratio. The complexes have been characterized by various physico-chemical techniques such as elemental analysis, molar conductance measurements, magnetic susceptibility measurements, infrared spectra and UV-Visible spectra. The complexes have been screened for their antibacterial activity against bacteria Escherichia coli MTCC 739, Staphylococcus aureus MTCC 96 and for antifungal activity against fungus Candida albicans MTCC 227.