A mononuclear GdIII Schiff base complex of formula [Gd(HL)2(NO3)3] (1), where HL = 2-methoxy-6-[(E)-phenyliminomethyl]phenol, has been isolated and its structure was determined by single-crystal X-ray diffraction. 1H NMR spectroscopic data reveal the zwitterionic nature of the HL ligand upon coordination with the GdIII ion. Direct current (dc) magnetic susceptibility and X-band EPR measurements were performed to probe the electronic and magnetic properties of complex 1. The susceptibility and magnetization data were fitted simultaneously, resulting in spin-Hamiltonian parameters: S = 7/2, g = 2.018, and D = 0.108 cm-1. The extracted parameters are in good agreement with the values obtained by fitting the temperature-dependent polycrystalline X-band EPR spectra of 1 (S = 7/2, g = 2.005, and D = 0.0815 cm-1; E/D = 0.08). EPR dilution experiments performed on 1 indicates strongly that the anisotropy arises solely from the GdIII ion with undetectably small or no contribution from spin-spin exchange interactions.