Titanyl phthalocyanine (TiOPc) is a well-known, excellent photoconductive material for laser printers and photocopying machines. Its organic derivatives have recently been shown to be excellent photosensitizers for singlet oxygen [O₂(¹Δ_g)] production. The excited triplet state properties of TiOPc, in homogeneous DMSO solution, were measured in this study for the first time by nanosecond laser flash photolysis. The data enabled comparisons to be drawn with TiOPcS₄ and zinc phthalocyanine (ZnPc), ultimately providing a better understanding of the reported observations. Absorption, fluorescence, and O₂(¹Δ_g) sensitization were also studied. TiOPcS₄ in DMSO shows remarkably different fluorescence properties from that reported in aqueous solution: both the fluorescence quantum yield (Φ_f = 0.068) and the fluorescence lifetime (τ_f = 3.71 ns) were much larger than that reported for aqueous solutions (0.012 and 0.09 ns, respectively). The photosensitizing properties of TiOPcS₄ in DMSO are also so significantly better than that in aqueous solution, i.e. triplet lifetime (τ_T) of 252 μs, triplet quantum yield (Φ_T) of 0.42, and the quantum yield of O₂(¹Δ_g) (Φ_Δ) of 0.49; compare with values of 60 μs, 0.32, 0.13 reported in aqueous solution. TiOPc, however, shows comparable photophysical properties to that of ZnPc, a well-recognized photosensitizer. These results suggest that TiOPc and its derivatives are not only good photoconductors but also good photosensitizers of O₂(¹Δ_g), which may find application in photodynamic therapies for treatment of cancer.