Beta-arrestins (beta arrs) critically mediate desensitization, endocytosis and signalling of G protein-coupled receptors (GPCRs), and they scaffold a large number of interaction partners. However, allosteric modulation of their scaffolding abilities and direct targeting of their interaction interfaces to modulate GPCR functions selectively have not been fully explored yet. Here we identified a series of synthetic antibody fragments (Fabs) against different conformations of beta arrs from phage display libraries. Several of these Fabs allosterically and selectively modulated the interaction of beta arrs with clathrin and ERK MAP kinase. Interestingly, one of these Fabs selectively disrupted beta arr-clathrin interaction, and when expressed as an intrabody, it robustly inhibited agonist-induced endocytosis of a broad set of GPCRs without affecting ERK MAP kinase activation. Our data therefore demonstrate the feasibility of selectively targeting beta arr interactions using intrabodies and provide a novel framework for fine-tuning GPCR functions with potential therapeutic implications.