We report that a polyhedral oligomeric silsesquioxane (POSS) core can enhance the entrapping ability of dendrimers. Compared to the G2 PAMAM dendrimer, the G2 POSS-core dendrimer can entrap a larger amount of guest molecules without loss of affinity, and consequently, the water solubility of the entrapped guest molecules can be increased. In addition, we demonstrated that a fluorophore entrapped in the G2 POSS-core dendrimer was prevented from undergoing fluorescence photobleaching.