Miranda vocabulary forms the essential foundation for Miranda comprehension and subsequent decisions to exercise or waive Miranda rights. The purpose of the current study is the development of the Miranda Vocabulary Scale (MVS), designed to evaluate key vocabulary words found in Miranda warnings and waivers across American jurisdictions. A preliminary list of MVS words was refined by expert ratings and by each word's discriminability between failed and good Miranda comprehension. Miranda and other measures were collected at multiple sites on 376 pretrial defendants. With further refinements, the MVS is composed of 36 words with excellent scale homogeneity and interrater reliability (r = .99). It also demonstrated good convergent and discriminant validity for cognitive abilities and psychological impairment.