In this study, the mononuclear Ni(II), Cu(II) and UO2(VI) complexes of N'-((2Z,3E)-3-(hydroxyimino) butan-2-ylidene)-2-phenylacetohydrazide ligand (LH2) have been synthesized. All compounds have been characterized by using elemental, spectral, X-ray analyses and magnetic moment measurements. The IR spectra of Ni(II) and UO2(VI) complexes show that LH2 has coordinated to the metal ions in tridentate manner with ON2 donor sites of deprotonated phenolic -OH, the imine N atoms of hydrazone (CO=N) and oxime (C=N-OH) groups. In the Cu(II) complex, the ligand is ketoamine form and bond to metal ion via carbonyl oxygen, imine nitrogen atoms of oxime and hydrazone groups. The spectral and magnetic studies show that the Ni(II), and Cu(II) complexes exhibit octahedral geometry. UO2(VI) complex has a monomeric structure constructed of a hexagonal bipyramidal uranyl centre with two monodentate ligand in trans-position. Newly complexes have been tested for antimicrobial and antioxidant activity. All of the complexes have active against L mono cytogenes, M. luteus, S. epidermis, B. cereus, S. typhi H, E. coli, Klebsiella pneumonia, Br. abortus and C albicans. Results of antioxidant activities indicate that the ligand and complexes have multiple antioxidant activities, such as total antioxidant (phosphomolybdenum) assay, reducing power, free radical (DPPH center dot), superoxide anion and ABTS' scavenging activity tests. The Ni(II) complex exhibited more effective total antioxidant activity and reducing power than BHA and trolox but weak the ABTS(center dot+), free radical (DPPH center dot), and superoxide anion (O-2(center dot-)) scavenging activity. The ABTS(center dot+), and DPPH* scavenging activities of Cu(II) were found excellent in comparison with standards. Ni(II), and UO2(VI) acted a powerful inhibitor of superoxide anion. The Cu(II) complex crystallized in the monoclinic space group C2/c, while UO2(VI) complex crystallized in the monoclinic space group P2(1)/c. (C) 2018 Elsevier B.V. All rights reserved.