Tridentate cycloplatinated thiosemicarbazone complexes have been prepared from a biologically significant ligand, 3,4-dichloroacetophenone thiosemicarbazone (1). The tetranuclear complex 2 was prepared by reaction of the ligand with K-2[PtCl4]. Two mononuclear (3 and 4) and two dinuclear (5 and 6) complexes were isolated upon cleavage of the Pt-S-bridging bonds of the tetranuclear complex 2 with the appropriate phosphane ligand. Each complex was characterized using various analytical and spectroscopic techniques, and the molecular structures of 2-4 were also elucidated. The in vitro antiparasitic activities of these complexes against Plasmodium falciparum strains (D10 (chloroquine sensitive) and Dd2 (chloroquine resistant)) and Trichomonas vaginalis have been determined. Preliminary studies into their potential plasmodial target in the form of beta-hematin formation inhibition assays were also completed. Preliminary results suggest that ligand 1 and complex 3 do not hinder formation of beta-hematin. The antiproliferative activity of the complexes against the cisplatin-senstive A2780 and cisplatin-resistant A2780cisR human ovarian cancer cell lines has been evaluated. The complexes were found to exhibit moderate to weak inhibitory activities.