AbstractA two‐photon pumped non‐linear optical (NLO) Fabry‐Pèrot (F‐P) type organic micro‐crystal resonator useful for a myriad of upconversion‐based light technologies is presented. The resonator is parallelepiped‐shaped and composed of a self‐assembled donor‐acceptor‐donor type molecule namely, 9,9,9”,9”‐tetramethyl‐9H,9’H,9”H‐[2, 2’:7,2”‐terfluoren]‐9’‐one (TTO). X‐ray crystal structure of an orange‐yellow TTO micro‐crystal reveals C−H⋅⋅⋅O type weak intermolecular hydrogen bond between the oxygen atom of the fluorenone unit and fluorine hydrogen atom. For one‐ and two‐photon excitation the micro‐crystals exhibit F‐P type modes in their photoluminescence signal. The fundamental frequency‐dependent NLO intensity shows a continuous increase as the fundamental wavelength is decreasing down to 770 nm. The two‐photon luminescence signals from these micro‐resonators are several orders of magnitude higher than the thin films of similar thickness.