Purpose: Worldwide, the burden of adverse health conditions is substantial among travestis and transgender women (trans women). Transcendendo, the first trans-specific cohort in a low- or middle-income country, is an open cohort established in August 2015 to longitudinally evaluate the health aspects of trans women aged ≥18 years in Rio de Janeiro, Brazil. Methods: Study visits occur on an annual basis. Data on sociodemographics, behavioral, gender transition, affirmation procedures, hormone use, discrimination, violence, clinical and mental health, HIV prevention, and care (for those HIV-infected) are collected. Physical examination, anthropometric measurements, and laboratory tests are performed. Results: As of July 2017, 322 trans women were enrolled in the cohort with a median age of 31.5 years (interquartile range 25.7-39.5), of whom 174 (54%) were HIV-infected. The Transcendendo baseline information reinforces the scenario of marginalization and deprivation surrounding trans women. Most participants had low income (62.0% were living with below US$ 10.00/day), showed a very high engagement in sex work (78.6%), and reported increased occurrence of sexual (46.3%) and physical (54.0%) violence. Pre-exposure peophylaxis (PReP) was used by 18.8% of the HIV-uninfected trans women, only through research participation. Positive screening for depression (57.8%) and problematic use of tobacco (56.6%), cannabis (28.9%), cocaine (23.8%), and alcohol (21.5%) were high. Almost all participants (94.8%) reported hormone use at some point, mostly without medical supervision (78.7%). Conclusion: Our results describe a context of exclusion experienced by trans women, exposing vulnerabilities of this population in a middle-income country, with poor access to trans-specific care, HIV prevention and care, and mental health care. Addressing transgender experiences and needs can help the development of strategies to diminish stigma, improve health care environment, guide future research on trans morbidities, substance use, and trans-specific interventions to support health-related recommendations. Ultimately, it contributes to close the gaps concerning transgender health and reinforces that trans care cannot be disentangled from the social environment that surrounds trans women.