We studied the relationship between the surface morphology and optical property of 9,10-bis(4-(N-carbazolyl)phenyl)anthracene (BCPA) nanocrystals having a small nanoparticle on their surface using an atomic force microscope (AFM) followed by density functional theory (DFT) calculations and optical spectroscopy. The estimated mean unit size of the small particles on the nanocrystal's surface in lateral terms was smaller than 20 nm, consisting of several thousand BCPA molecules. The fine structure observed in the emission spectrum of e-BCPA would be assigned to the vibronic transitions of BCPA molecules.