Significance Approximately one-third of eukaryotic proteins are synthesized on ribosomes attached to the endoplasmic reticulum (ER) membrane. Many of these polypeptides co- or posttranslationally translocate into the ER, wherein they fold and mature. An ER quality control system proofreads these proteins by facilitating their folding and modification, while eliminating misfolded proteins through ER-associated degradation (ERAD). Yet the fate of many secretory proteins during ER stress is not completely understood. Here, we uncovered an ER stress-induced “protein reflux” system that delivers intact, folded ER luminal proteins back to the cytosol without degrading them. We found that ER protein reflux works in parallel with ERAD and requires distinct ER-resident and cytosolic chaperones and cochaperones.