Background: High work demands and low work resources predispose employees to occupational burnout. Burnout of Sri Lankan prison officers has not been studied previously. Prison guards and prison rehabilitation officers are the staff categories who come into regular and direct contact with prison inmates. Aim: The study aimed to describe the prevalence of burnout and its three sub-domains in Sri Lankan prison officers and to explore the personal and work-related correlates of their burnout. Methods: An institution-based cross-sectional study was carried out in 2017, among 1803 prison officers including 1683 prison guards and 120 prison rehabilitation officers working in 32 prison institutions island-wide. Prison guards were selected using multi-stage stratified sampling, while all the eligible Rehabilitation Officers were included. Self-administered, translated and validated Sinhala version of the Maslach Burnout Inventory – Human Services Survey and a self-developed questionnaire on correlates were used for collecting data. Results: The response rate was 98.53%. Majority of the participants were male (88%) and currently married (80.6%). True prevalence of burnout was 31.1% (95%CI:22.1-40.1). More than one third (37.8% - 95%CI:28.3–47.3) were suffering from diminished personal accomplishment, while over one fourth were suffering from emotional exhaustion (28.6% - 95%CI:19.7–37.5) and depersonalization (26.9% - 95%CI:18.2–35.6). Feeling overburdened by housework (OR–3.9,95%CI:1.6-9.3), working in closed prisons (OR–5.4,95%CI:1.3–21.7), remand prisons (OR–4.9,95%CI:1.2–19.3) and work camps (OR–6.7,95%CI:1.6–28.4), perceived difficulty in shift work (OR–2.4,95%CI:1.4–4.0) and in taking leave (OR–2.8,95%CI:1.5–5.4), work overload (OR–2.1,95%CI:1.1–3.7), poor relationship with colleagues (OR–10.6,95%CI:1.1–103.3) and with families of inmates (OR–4.7,95%CI:1.4–16.0), poor welfare facilities (OR–3.8,95%CI:1.6–8.7) and job dissatisfaction (OR:14.3,95%CI:4.4–46.8) were associated with a higher risk for burnout. Conclusion: Burnout among prison officers is a significant issue requiring prompt interventions including basic and in-service trainings focusing on stress management.