The substituent effect at the C6-position of 1,3a,6a-triazapentalenes was elucidated. Synthesis of C6-substituted-1,3a, 6a-triazapentalene was established by an epoxide-opening reaction of the 1,2,3-triazoles followed by elimination of the resulting hydroxy group. The electron-donating substituent induced a longer-wavelength shift of the fluorescence maximum and change of the fluorescence quantum yield depending on the C2-substituents. On the other hand, the electron-withdrawing group quenched the fluorescence of 1,3a, 6a-triazapentalenes.