Oxoplatin-B, a platinum(IV) complex [Pt(NH)Cl(L)(OH)] (1) of 4-methylbenzoic acid (HL) functionalized with 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) was prepared, characterized and its antitumor activity studied. [Pt(NH)Cl(L)(OH)] (2) of 4-methylbenzoic acid (HL) was studied as a control. Complex 1 showed an absorption band at 500 nm (ɛ = 4.34 × 10 M cm) and an emission band at 515 nm (λ = 488 nm, Φ = 0.64) in 1% dimethyl sulfoxide/Dulbecco’s Modified Eagle’s Medium (pH = 7.2). Visible light-induced (400-700 nm) generation of singlet oxygen was evidenced from 1,3-diphenylisobenzofuran titration study. Complex 1 showed photo-induced cytotoxicity in visible light (400-700 nm, 10 J cm) against human breast cancer (MCF-7), cervical cancer (HeLa) and lung cancer (A549) cells (IC: 1.1-3.8 μM) while being less toxic in normal cells. Confocal imaging showed mitochondrial localization with additional evidence from platinum content from isolated mitochondria and 5,5,6,6′-tetrachloro-1,1′,3,3′ tetraethylbenzimi-dazoylcarbocyanine iodide (JC-1) assay. Cellular apoptosis was observed from Annexin-V-FITC (fluorescein isothiocyanate)/propidium iodide assay.