Isoniazid, an anti-tuberculosis (TB) drug has been coordinated with chromium, molybdenum, and tungsten metal carbonyls and three new zero-valent complexes fac-[M(CO)3(isoniazid)3] (M = Cr, Mo, and W; 4, 5, and 6) (isoniazid = 4-H2NHNOCC5H4N) have been synthesized. Reaction of the complex precursors fac-[M(CO) 3(CH3CN)3] (M = Cr, Mo, and W; 1, 2, and 3) prepared 'in situ' with three equivalents of isoniazid in methanol at room temperature afforded high yields of isoniazid substituted metal carbonyl complexes 4, 5, and 6. The complexes have been characterized by elemental analyses, mass analysis, thermal analysis (TGA, EGA), FT-IR, UV/visible and 1H NMR spectroscopic techniques and powder X-ray diffraction (XRD). The FT-IR (KBr and methanol solution) spectra of the complexes 4, 5, and 6 exhibit two bands corresponding to v(C≡O) of metal carbonyl groups and v(C=O) of coordinated isoniazid molecules. The bulky -CONHNH2 group of isoniazid molecules made more impact on the M-C bond strength of metal carbonyls and affects their fundamental modes of vibrations leading to the appearance of more number of v(C≡O) bands. These steric effects are also reflected in the 1H NMR spectral features of the complexes when considering the complexes as a whole, wherein the four protons on the pyridine ring of the coordinated isoniazid molecules resonate at different chemical shifts. All the three complexes exhibit similar XRD pattern suggesting similar geometry.