Core-crosslinked micelles (CCMs) with a hydrophilic polyanionic shell made of poly(sodium styrene sulfonate) chains, P(SS−Na$^+$), a triphenylphosphine oxide-functionalized polystyrene core (TPPO@PSt) and crosslinked at the inner end of the polystyrene chains by diethylene glycol dimethacrylate (DEGDMA) were synthesized by reversible addition-fragmentation chain-transfer (RAFT) polymerization as a stable TPPO@CCM-A latex. One-pot synthesis of rhodium nanoparticles (RhNPs) by the reduction of [Rh(COD)(μ-Cl)]₂ in the aqueous TPPO@CCM-A latex yielded a stable RhNP-TPPO@CCM-A latex without the need of additional stabilizer or base. This Rh-loaded latex was applied to the catalytic biphasic hydrogenation of styrene under mild conditions with complete selectivity towards ethylbenzene and corrected turnover frequencies (cTOFs) ranging from 3250 to 10,010 h$^{−1}$ based on the surface atoms of the RhNPs. Importantly, the catalytic phase proved recyclable after product extraction, owing to the efficient retention of the RhNPs by the core TPPO ligands.