Achieving organic red/near infrared (NIR) phosphorescence at high temperatures is theoretically challenging because of the severe nonradiative transitions of excited triplet states with low energy gaps. This study realizes bright and persistent red/NIR afterglow with excellent high-temperature resistance up to 413 K via highly efficient (≈100%) phosphorescence resonance energy transfer (PRET) from rationally designed branched phosphorescence luminogens as energy donors to red/NIR dyes as acceptors, coupled with optimized aggregated structures. According to systematic investigations, the abundant internal cavities formed by the highly branched luminogens in solid states ensure dye loading and space limitation, which can considerably suppress nonradiative transitions at high temperatures, promoting a persistent red/NIR afterglow with excellent stability. Moreover, 16 types of host-guest systems with varied topological structures of branched luminogens and different red/NIR dyes of various sizes confirm the universality of the strategy. This study provides an efficient approach to achieve a highly stable red/NIR afterglow.