We report a systematic study of the nonlinear absorption characteristics of pi-conjugated chromophores using density functional theory (DFT), namely, the prediction of singlet-triplet splittings (S-0-T-1), vertical triplet-triplet (T-1-T-n) excitation energies, and corresponding oscillator strengths. This is a first application of DFT/time-dependent DFT to a broad range of pi-conjugated test molecules for the prediction of the T-1-T-n excitation energies and oscillator strengths and the S-0-T-1 energies, using Becke's three-parameter hybrid functional. Our results show a good agreement with experimental excitation energies and oscillator strengths. The range of errors obtained from the computed results is discussed in detail.