In the present work, the influence of serum albumins as biological hosts on the well-established photo-Fries rearrangement has been investigated. For this purpose, 4-methoxy-1-naphthyl hydrogen succinate and glutarate (1a,b) as well as the corresponding acetate (1c), have been selected as substrates. Special attention has been devoted to the effect of the binding site location and serum albumin species on the outcome of the reaction. In a first stage, the stabilizing effect of the biomacromolecule on the intramolecularly catalyzed hydrolysis of succinate 1a was observed. Then, 1b and 1c were considered for their interaction with proteins in site II and site I, respectively. Site assignment was confirmed by fluorescence displacement experiments with dansylamide and dansylglycine. Moreover, spectroscopic analysis showed a site dependent quantum yield of product formation for human and bovine serum albumin.