Poly(aryl ether) dendrimers of three different generations (n = 1, 2, 3) that are cored with phototautomerizable quinoline (QGn) were synthesized to investigate the effect of dendritic architecture on the excited-state intramolecular proton transfer (ESIPT). It was deduced from the generation-dependent absorption spectra that the peripheral crowdedness arising from the dendritic structure not only decouples the ESIPT core from the molecular surrounding but also influences the core planarity. Static and picosecond kinetic studies on ESIPT emission provided further information that the ESIPT in the quinoline core is slowed down with increasing dendrimer generation via the reduced core planarity. However, it was also observed that the proton transfer is still so effective even in the highest generation dendrimer that the emission efficiency is largely increased with dendrimer generation through the enhanced isolation effect. Compared to the polystyrene blend film containing nondendritic model compound (MQ), the films of QGn were proven to be a truly single-component "solid solution" with better performances in terms of the emission efficiency and chromophore content.