A practical arsenic halogenation of 9-arsafluorene, which can be safely and easily prepared from a cyclooligoarsine, was developed by using halogen sources such as iodine and iodine monochloride. The in situ prepared 9-halogeno-9-arsafluorenes reacted with various nucleophiles to provide 9-arsafluorene derivatives. The functional groups affected their emission properties in the solid state through changes in the packing structure. To estimate the reaction mechanism of the halogenation, density functional theory calculations were employed; the molecular behaviors of oxidative addition and reductive elimination on the arsenic atom were elucidated. Furthermore, the present reaction was applied to a structure other than 9-arsafluorene as well.