The fluorescence properties of ethyl p-(N,N-diethylamino)benzoate (DEAEB) are studied in the vapor phase, supercritical fluids, and room-temperature solutions. Dual emission in the vapor phase due to the formation of a twisted intramolecular charge-transfer (TICT) state is observed. Relative emission contributions of the locally excited (LE) and TICT states are determined for DEAEB under different conditions by applying chemometric spectral resolution methods to observed dual fluorescence spectral mixtures. The TICT emission contribution accounts for 27 +/- 5% of the total fluorescence in the vapor phase and 80-97% in room-temperature solutions. Decays of the TICT state are strongly solvent dependent and follow the energy gap relationship from radiationless decay theories. For DEAEB in alcohol and aqueous solutions, the small fluorescence quantum yields are attributed to fluorescence quenching that is associated with specific solute-solvent interactions such as hydrogen bonding.