A novel self-complementary nucleoside ((A)T), featuring two complementary nucleobases linked through an ethynyl group has been synthesized. The rigid aromatic nucleobases provided (A)T with a pale-blue fluorescence. Unlike most fluorescent organic molecules, nucleoside (A)T gives enhanced fluorescence in solid state. It exhibits considerably enhanced fluorescence intensity and a remarkable redshift (ca. 70 nm) in its emission maximum upon an increase in concentration or decrease in temperature as a result of the formation of aggregates stabilized through hydrogen bonding and π-π stacking of well-organized (A) T assemblies; these interactions are also evident in the solid-state structure, determined by X-ray crystallography. DFT calculations supported the preference of such aggregation processes.