For improving functional and exploitation characteristics of the poly(phenylene oxide) (PPO) gas separation membrane, it was loaded with nitrogen-doped carbon quantum dots (CQDs) (0.5–1.5 wt%). The latter were synthesized from citric acid and L-phenylalanine via a one-step hydrothermal method. Both PPO and PPO/CQDs materials were studied with scanning electron microscopy; UV–vis, FTIR, and XPS spectroscopy techniques; and subjected to mechanical tests. The selectivity in the He/N2 and O2/N2 gas pair separation was shown to increase with increasing CQDs content in the PPO/CQDs membranes. Meanwhile the permeation of individual He, O2, and N2 gases through the PPO/CQDs membranes decreases with increasing CQDs content since the CQDs incorporation into the PPO matrix increases the density of the films and decreases their free volume.