The effect of temperature on naphthalene solubilization in aqueous PEO-PPO-PEO block copolymer solutions has been investigated. Increasing temperature would enhance the apparent solubility of naphthalene in aqueous PEO-PPO-PEO block copolymer solutions. The pseudo-phase model was employed to calculate thermodynamic parameters for naphthalene solubilization in aqueous PEO-PPO-PEO block copolymer solutions.