Historically developed along gender lines and arguably the most sex segregated of institutions, U.S. prisons are organized around the assumption of a gender binary. In this context, the existence and increasing visibility of transgender prisoners raise questions about how gender is accomplished by transgender prisoners in prisons for men. This analysis draws on official data and original interview data from 315 transgender inmates in 27 California prisons for men to focus analytic attention on the pursuit of "the real deal"—a concept we develop to reference a dynamic related to how gender is accomplished by transgender inmates. Specifically, among transgender inmates in prisons for men, there is competition for the attention and affection of "real men" in prisons: the demonstrable and well-articulated desire to secure standing as "the best girl" in sex segregated institutional environments. Our empirical examination sheds light on the gender order that underpins prison life, the lived experience of gender and sexuality for transgender inmates in prisons for men, and how that experience reveals new aspects of the workings of gender accountability.