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We have prepared and characterized seven new nickel(II) complexes that each incorporate tris(2-aminoethyl)amine (tren) and a deprotonated carbonyl-containing compound, both as two separate ligands and when condensed into a 1:1 Schiff-base ligand. We found the application of an existing literature procedure to be unsuccessful in procuring the Schiff-base variants without first assembling the ligand. IR, UV–VIS, magnetic susceptibility, elemental, and melting point data were obtained for the complexes prepared. Three of these compounds were also characterized through X-ray diffraction, and the resulting crystal structures are presented here for [Ni(acac)(tren)]BPh4 (1), [Ni(trensal)(OH2)]ClO4 (5), and [Ni(trenvan)]BPh4·H2O (7) ([acac]- = acetylacetonate ligand, [trensal]- = deprotonated 1:1 condensation product of tren and salicylaldehyde, [trenvan]- = deprotonated 1:1 condensation product of tren and ortho-vanillin). We also screened a selection of the complexes for biological activity. Two of the complexes, [Ni(trenacac)]BPh4 (4) and [Ni(trensal)]BPh4·½H2O (6) were found to fully inhibit the growth of the pathogenic yeast Candida albicans at the sub-micromolar concentration range ([trenacac]- = deprotonated 1:1 condensation product of tren and acetylacetone).