The complexations of sulfasalazine (H 3 Suz) with some of transition metals have been investigated. Three types of complexes, [Mn(HSuz) -2 (H 2 O) 4 ]⋅2H 2 O, [M(HSuz) -2 (H 2 O) 2 ]⋅xH 2 O (M = Hg(II), ZrO(II) and VO(II), x = 4, 8 and 6, respectively) and [M(HSuz) -2 (Cl)(H 2 O) 3 ]⋅xH 2 O (M = Cr (III) and Y(III), x = 5 and 6, respectively) were obtained and characterized by physicochemical and spectroscopic methods. The IR spectra of the complexes suggest that the sulfasalazine behaves as a monoanionic bidentate ligand. The thermal decomposition of the complexes as well as thermodynamic parameters (ΔE*, ΔH*, ΔS* and ΔG*) were estimated using Coats-Redfern and Horowitz-Metzger equations. In vitro antimicrobial activities of the H 3 Suz and the complexes were tested.