Photochromic diarylethene derivatives having different lengths and numbers of poly(ethylene glycol) side chains were synthesized and their photochromic property and self-assembling behavior were investigated. The self-assembling behavior of the derivatives strongly depends upon the ratio between the hydrophobic core and the amphiphilic side chain. According to UV/Vis absorption spectroscopy, CD spectroscopy, and dynamic light scattering experiments, these derivatives showed different size distribution of the assembled structures and different solubility in water. The intensity of the induced CD signal, which was observed in the closed-ring isomer, was the largest for the molecule having two hexaethylene glycol side chains. The relationship between the core-chain ratio and regularity of the self-assembled structure has been investigated.