γ-secretase is a transmembrane protease complex responsible for processing multiple type I transmembrane proteins, including the amyloid precursor protein and NOTCH. Despite various γ-secretase inhibitors and modulators developed in the past decades to target Notch-dependent cancers, their clinical use is still limited due to the low substrate specificity and on-target gut toxicity. Using a proteomics-based screening approach, we found that the dedicator of cytokinesis protein 2 (DOCK2) interacts with the γ-secretase complex component Nicastrin, regulating Nicastrin N45-mannosidation and γ-secretase activity towards NOTCH receptors.