Suicide has been recognized as one of the commonest causes of death globally and mental disorders and found to contribute about 70% to 80% of causes of suicide. A number of factors can predict or increase the risk of suicide among those who have mental illnesses. This study aimed to determine the pattern and prevalence of suicidal behaviour among those with mentally illness at the University of Port Harcourt Teaching Hospital. This was a descriptive cross-sectional study conducted among attendees of Neuropsychiatric Outpatient Clinic of the University of Port Harcourt Teaching Hospital. A structured questionnaire covering socio-demographic characteristics and other factors were self-administered to 75 patients diagnosed with various psychiatric disorders via a systematic random sampling. Ethical approval was obtained from the relevant ethical committee. Descriptive statistics was used to analyze the data. Majority of the respondents were male (81%), single (76.0%), unemployed (36.0%), low income earners (73.4%) and between the ages of 21 and 30 (44%). Majority had tertiary education (58.7%) followed by respondents with secondary education (33.3%). The most common psychiatric presentation include depression 19(25.3%), followed by anxiety disorder 16(21.3%), BAD 12(16.0%), substance misuse 9(12.0%) and schizophrenia 11(14.7%), Nineteen (25,3%) of the respondents has had suicidal thoughts while 7(9.3%) had attempted suicide. The commonest method employed was ingestion of poison. Suicide behaviour was common among those with mental illness including substance use disorder, unemployment,  feeling of stigmatization, poor premorbid history, and adverse childhood experience. Mental illness worsened by other psychosocial factors is a common predictor for suicide behavior. It is therefore important to provide adequate attention and care to the mentally ill to help reduce the prevalence of suicidal haviour among them.  

Key words: Pattern, Suicide Behaviors, Mentally Ill, South-South Nigeria