We developed a new system for light-induced protein dimerization in living cells using a photocaged analogue of rapamycin together with an engineered rapamycin binding domain. Using focal adhesion kinase as a target, we demonstrated successful light-mediated regulation of protein interaction and localization in living cells. Modification of this approach enabled light-triggered activation of a protein kinase and initiation of kinase-induced phenotypic changes in vivo.