Protein:protein interactions are among the most difficult to treat molecular mechanisms of disease pathology. Cystine-dense peptides have the potential to disrupt such interactions， and are used in drug-like roles by every clade of life， but their study has been hampered by a reputation for being difficult to produce， owing to their complex disulfide connectivity. Here we describe a platform for identifying target-binding cystine-dense peptides using mammalian surface display， capable of interrogating high quality and diverse scaffold libraries with verifiable folding and stability. We demonstrate the platform's capabilities by identifying a cystine-dense peptide capable of inhibiting the YAP:TEAD interaction at the heart of the oncogenic Hippo pathway， and possessing the potency and stability necessary for consideration as a drug development candidate. This platform provides the opportunity to screen cystine-dense peptides with drug-like qualities against targets that are implicated for the treatment of diseases， but are poorly suited for conventional approaches.