Introduction: Sex workers face many barriers to accessing the inalienable human right of mental health. The aim of this review was to synthesize the evidence on the barriers to mental healthcare for sex workers and the factors that facilitate uptake. Methods: A search conducted in 2018 of peer-reviewed and gray literature produced between 2008 and 2018 in OECD countries resulted in 32 documents eligible for inclusion. Results: The literature revealed that the barriers of stigma, discrimination, violence, pathologization, and criminalization exacerbate the psychological distress of sex workers while impeding uptake of mental healthcare. Personal resilience, protective factors, agency, and social inclusion offset these barriers. Conclusions: Despite the risk of pervasive mental illness among sex workers due to, primarily, external factors, few studies present comprehensive examinations of sex workers’ mental health and fewer still explore sex workers with gender identities and sexual orientations that are not cisgender, heterosexual, or female. Policy Implications: Although timely, equitable treatment of sex workers in mental healthcare is currently atypical, the findings of this review suggest that inclusive, respectful psychological care is possible. Future research on holistic approaches to the mental health of sex workers could support the creation of much-needed, inclusive services and policies that improve sex workers’ quality of life.