AbstractThe increase in migratory flows worldwide has led to the creation of detention centers as a form of control of irregular migration. Recipient countries are responsible for protecting detainees’ right to mental health, but the literature suggests that immigration detention centers are environments associated with complex mental health needs among the detainees. This study aims to approach the mental health of people detained in the immigration detention centers in Spain, a southern border of Europe. Eighty-seven migrants coming from different Latin American and African countries were interviewed using an adaptation of the Measure of Quality of Life in Detention (MQLD; Bosworth & Gerlach, 2020) to measure the perceived detention environment and The Hopkins Symptom Checklist-25 (HSCL-25; Derogatis et al., 1974) to assess mental health. The results show a high prevalence of detainees with significant levels of anxiety and depression (69%) and attempts at self-harm within the detention centers (19.5%). A more positive perception of the detention environment—especially concerning institutional decency and the relationship with officers—is related to a lower degree of negative mental health symptoms. Finally, people detained for more than 2 weeks assess the detention environment more negatively than those detained for less time. Scientific contributions and social implications to ensure the mental health of detainees from a human rights-based approach are discussed.