We have observed very bright visible luminescence from N-isopropylcarbazole (NIPCz) when the compound crystallizes from the molten state to a crystalline aggregate. The sample crystals were heated on a glass plate to above their melting point (380 K) and cooled gradually under ambient conditions. When their temperature fell below 350 K, sudden rapid crystallization took place, accompanied by bluish-white luminescence. Video imaging of the phenomena revealed that both the crystallization and luminescence occurred in the same time frame of <0.5 ms, demonstrating that the two effects were intimately related to each other, i.e., crystalloluminescence (XTL). Thermal analysis of the sample revealed that the preceding state prior to the crystallization was not a glassy solid, but a supercooled liquid state. The XTL spectrum agreed very well with both photo- and triboluminescence spectra of NIPCz. Moreover, its intensity was considerably higher than the reported values for other crystalloluminescent materials such as NaCl. This is the first demonstration of the fluorescent XTL of an organic material. We discussed the mechanism leading to XTL in detail on the basis of the available models, and we concluded that a valid explanation for XTL could be provided by triboluminescence mechanisms.