IntroductionThe coronavirus disease is still not under the control globally and has caused various mental health problems such as depression, anxiety, suicide, and aggressive behavior in different populations. The pandemic-related issues which are applied to control the pandemic such as protection measures against COVID-19, social distancing, isolation, and quarantine can also trigger mental health problems.ObjectiveThis study aimed to assess suicidal behavior and aggression, and its correlates during COVID-19 among populations within institutional quarantine and isolation centers in Ethiopia.MethodA cross-sectional study was conducted among a sample of 392 participants. The convenience sampling method was used to select the study participants. Suicide Behavioral Questionnaire-Revised (SBQ-R) and the Modified Overt Aggression Scale (MOAS)were applied to determine the suicide and aggressive behavior of study participants respectively. Epi-data 3.1 and SPSS 20.0were used to enter and analyze the data respectively. Logistic and linear regressions were fitted to explore correlates associated with suicidal behavior and aggression respectively.ResultsThe prevalence of suicidal behavior was 8.7% (95% CI: 6.1, 11.5) whereas the mean total score of behavioral aggression was 2.45±5.90 (95% CI: 1.84, 3.08). Being female (AOR = 2.63, 95% CI: 1.09, 6.32), having common mental disorders (AOR = 6.08, 95% CI: 2.32, 15.93), manifesting the symptoms of COVID-19 (AOR = 2.17, 95% CI: 1.48, 2.86), and poor social support (AOR = 7.30, 95% CI: 1.44, 37.10) were significantly associated with suicidal behavior, whereas male gender (β coefficient = 3.0, 95% CI: 1.35, 4.70), low level of knowledge about COVID-19 (β coefficient = 1.87, 95% CI: 1.09, 3.41), and substance use (β coefficient = 1.7, 95% CI: 1.23, 6.47) were positively associated with mean overt aggression score.ConclusionThe present study revealed that suicidal and aggressive behaviors were prevalent with significant correlates. Therefore, it is important and required to provide focused mental health and psycho-social services for the selected and high-risk populations such as those in quarantine and isolation centers for being suspected.