In biological systems, chiral self-assemblies are formed in water. To understand the role of water in the formation of supramolecular chirality, an amino acid derivative, N,N-diphenylalanine-3,4,9,10-perylenetetracarboxylicdiimide (PBI-Phe), was synthesized from perylene-3,4,9,10-tetracarboxylic dianhydride and phenylalanine. PBI-Phe self-assembled into a spherical structure in pure DMSO, but into a helical fiber structure in a solution of DMSO mixed with water. Furthermore, increasing the relative amount of water included in the solution led to an increase the supramolecular chirality.