Background: incarceration and mental health problems are empirically known to have a strong association. Many studies have confirmed the high prevalence of mental health problems among young prisoners in particular, yet none have been conducted in Cambodia. Objectives: this study aimed first to assess the prevalence of mental health problems and suicidal expressions among young prisoners, and second, to determine the risk factors associated with these two outcomes in Cambodia. Method: a cross-sectional study among 572 young male prisoners between the ages of 15 and 24 from three prisons was conducted. Sociodemographic data and detailed information on participants’ profiles were gathered, and the Youth Self-Report (YSR) and the Attitude towards Suicide (ATTS) questionnaires were applied. Results: anxiety-depression affected 52.10% of the respondents with a similar prevalence of withdrawal depression, somatic complaints, social problems, and aggressive behaviours (around 46%). Mental health problems were strongly associated with younger age, lower educational background, and less time spent in prison. Around half (51.05%) considered life to be meaningful while 16.26% had thoughts about their own death, and 12.06% expressed wishes to die. Suicide ideation, planning, and attempts were reported by almost 6.82%, 1.75% and 2.80% of participants respectively. Prisoners who used drugs prior to imprisonment thought about death significantly more than their counterparts while suicide ideation was reported to be significantly lower among prisoners with higher education. Conclusion: the prevalence of mental health problems among young male prisoners was considerably high, while suicide expressions were reported to be lower compared to studies from other countries. This study highlights the need for implementing preventive interventions integrated into the prison health care system to improve the mental health of young prisoners.