Nickel(II) complex of 4,4,4-trifluoro-1-(2-Naphthyl)-1,3-butanedione(tfnb) and its 2,2′-bipyridine (bipy), ethylenediamine (en) and 1,10-phenanthroline (phen) adducts were synthesized and characterized by elemental analysis, infrared, electronic spectral, magnetic susceptibility measurements and antimicrobial activities. Three other nickel(II) compounds were synthesized along with these compounds. The bands in the 1651-1513 cm-1 have been assigned as ν(C=O) + ν(C=C). The infrared and electronic spectral measurements are indicative of a probable six-coordinate octahedral geometry for all the nickel(II) complexes and adducts. The antimicrobial activity shows that [Ni(tfnb)2]2H2O complex and its adducts have no antibacterial and antifungal activities.