The correct functioning of any protein depends in its accurate localization, particularly for membrane proteins, as they control the selective transport of molecules across specific membranes. Newly synthesized membrane proteins transit from its place of synthesis, the endoplasmic reticulum, to the Golgi apparatus, employing a vesicular system known as COPII. Formation of COPII vesicles is required for the selective packaging of membrane proteins through the coordinated participation of the Sec24 subunit and cargo receptors, where cornichon proteins have been identified as playing a central role. The functioning of cornichon proteins is conserved from yeast to vertebrates, but it is poorly characterized in plants. We analysed the role of the two cornichon homologs present in the moss Physcomitrium patens by generating single and double mutants. Our results revealed that cornichon proteins regulate different growth processes during the moss life cycle by controlling auxin transport, with PpCNIH2 functioning as a specific cargo receptor for the auxin efflux carrier PINA. Additional characterization demonstrated that the C-terminus of PpCNIH2 regulated the interaction, trafficking and membrane localization of PINA.