HIV-infected individuals leaving jails, facilities typically used to confine accused persons awaiting trial or to incarcerate persons for minor offenses, often face barriers to engagement with medical and social-support services. Patient navigation is a model that may ease these barriers by supporting individuals in negotiating fragmented and highly bureaucratic systems for services and care. While there is evidence linking navigation to a reduction in health disparities, little is known about the mechanisms by which the model works. We present findings of an ethnographic study of interactions between navigators and their clients: HIV-infected men and women recently released from jails in San Francisco, California. We conducted 29 field observations of navigators as they accompanied their clients to appointments, and 40 in-depth interviews with clients and navigators. Navigators worked on strengthening clients' abilities to engage with social-services and care systems. Building this strength required navigators to gain clients' trust by leveraging their own similar life experiences or expressing social concordance. After establishing meaningful connections, navigators spent time with clients in their day-to-day environments serving as mentors while escorting clients to and through their appointments. Intensive time spent together, in combination with a shared background of incarceration, HIV, and drug use, was a critical mechanism of this model. This study illustrates that socially concordant navigators are well positioned to facilitate successful transition to care and social-services engagement among a vulnerable population.