Novel azobenzene-functionalized hydroxypropyl methylcellulose (AZO-HPMC) polymers and their alpha-cyclodextrin (alpha-CD) complexes have been prepared. These polymers show interesting sol-gel transition behavior in aqueous solutions. In the absence of alpha-CD, the gelation temperature increases after UV irradiation, while in the presence of alpha-CD, the gelation temperature decreases after UV irradiation. The difference in the gelation temperatures between the trans and cis samples of AZO-HPMC opens a wide operating window for reversible-regulation of the sol-gel transition behavior by photoirradiation.