The valence photoisomerization of four aromatic norbornadiene (NBD) derivatives has been studied in ethanol and in 0.01 M β-cyclodextrin (β-CD) water–ethanol (v/v, 99/1) solution (WECD). Observed first-order rate constants are found to be of the same order of magnitude in ethanol and WECD, ranging between 0.1 and 0.28 s-1, according to the compound. These photoisomerization kinetic properties are attributed to the formation of inclusion complexes between NBDs and β-CD. The stoichiometry is 1:1, and association constants ranging between 310 and 390 M-1 have been determined fluorimetrically, using Benesi–Hildebrand plots and a nonlinear regression method. The structure of the inclusion complexes is discussed on the basis of AMI semiempirical dimension calculations and photophysical properties.