A new Schiff base 3-[3-(hydroxyimino)butan-2-ylidene]hydrazinylidene}methyl]phenol) has been synthesized by the condensation of m-hydroxybenzaldehyde and diacetylmonoximehydrazone (1:1 molar ratio). Its complexes with trivalent lanthanides (La3+, Nd3+, Sm3+, Gd3+, Tb3+ and Dy3+) have been synthesized. The ligand has two coordination sites, azomethine and oximinonitrogens take part in coordination. The complexes have been assigned the general formula [Ln(DMHmHB)2NO3] on the basis of elemental analysis, molar conductance, magnetic moment, PMR, electronic absorption and FT(IR) spectral studies. The electronic spectra of the complexes of La3+, Nd3+, Sm3+, Gd3+, Tb3+ and Dy3+ have been analyzed and discussed. The spectral parameters show covalent nature of bonding between the metal and the synthesized ligand.