Simultaneous two-photon excitation of a solution mixture of [Ru(dmb)(3)](2+) and 9,10-diphenylanthracene (DPA) using 860 nm light pulses from a Ti:Sapphire laser resulted in triplet energy transfer followed by triplet-triplet annihilation (TTA), ultimately leading to upconverted DPA fluorescence from the sensitized DPA triplets. The photochemistry sequence was confirmed by the unprecedented quartic (x(4)) incident light power dependence exhibited by this process, which incidentally generated a record anti-Stokes shift of 1.38 eV for sensitized TTA.