Crystals of 4-dimethylaminoazobenzene-4′-sulfonyl-L-tryptophan dimethylsulfoxide solvate (Dabs-Trp·DMSO) are monoclinic, space group P2₁ with a = 12.941(6)Å, b = 7.760(3)Å, c = 14.131(7)Å, β = 103.161(8)° and Z = 2. The structure was solved by direct methods (SIR88) and refined to a final R value of 0.058 for 3152 reflections (I > 2.00σ(I)). The molecular geometries and conformations are comparable to the typical values of azobenzene and L-tryptophan. The DMSO molecule is involved in the intermolecular hydrogen bonds with the sulfonamide NH and the carboxyl OH groups of different Dabs-Trp molecules. The hydrogen-bonded chains propagate along the b axis, and are constructed from molecules related by a two-fold screw axis. The sulfonamide S=O and the carboxyl C=O groups do not participate in hydrogen bonding.