The United Kingdom has one of the largest systems of immigration detention in Europe. The majority of those detained are asylum seekers and foreign national prisoners in immigration removal centers (IRCs). Previous research has identified that this population is particularly vulnerable to mental health disorders compared with the general population. The primary aim of this study was to assess the feasibility of conducting psychiatric research in IRCs. The secondary aim was to compare rates of psychiatric morbidities to those of other populations. The current study used a cross-sectional study design with a sample of 101 detainees from a single IRC in the United Kingdom. Consenting participants underwent an interview process comprising six validated psychiatric screening tools for common mental health and developmental disorders (e.g., depression, personality disorder and autism), as well as a needs assessment. All researchers were trained in the battery of assessments, and inter-rater reliability was assessed by joint ratings. The study achieved a 39% response rate and found the most prevalent mental health disorder to be depression (52.5%), followed by personality disorder (34.7%) and post-traumatic stress disorder (PTSD; 20.8%). A total of 21% were found to be at a moderate-to-high risk of suicide. The greatest unmet needs among inmates concerned intimate relationships (76.2%), psychological distress (72.3%), and sexual expression (71.3%). The prevalence of mental health disorders found in the current study is comparable to results found within prisons. The present study demonstrates the feasibility of conducting psychiatric research within IRCs. Methodological limitations are discussed to facilitate future research.