Background. Suicide is a serious cause of mortality worldwide and is considered as a psychiatric emergency. Suicide is more frequent in peoples living with HIV/AIDS than in general population. Objective. To assess the proportion and determining factors of suicidal ideation and attempt among peoples living with HIV/AIDS in Ethiopia. Methods. Institutional based cross-sectional study was conducted from May to June 2015 by selecting 393 participants using systematic random sampling technique. Suicide manual of Composite International Diagnostic Interview (CIDI) was used to collect data. Logistic regression was carried out and odds ratio with 95% confidence intervals was computed. Results. The proportion of suicidal ideation and attempt was 33.6% and 20.1%, respectively. Female sex (AOR = 2.6, 95%CI: 1.27–5.22), marital status (AOR = 13.5, 95%CI: 4.69–39.13), depression (AOR = 17.0, 95%CI: 8.76–33.26), CD4 level (AOR = 2.57, 95%CI: 1.34–4.90), and presence of opportunistic infection (AOR = 5.23, 95%CI: 2.51–10.88) were associated with suicidal ideation, whereas marital status (AOR = 8.44, 95%CI: 3.117–22.84), perceived HIV stigma (AOR = 2.9, 95%CI: 1.45–5.99), opportunistic infection (AOR = 2.37, 95%CI: 1.18–4.76), and poor social support (AOR = 2.9, 95%CI: 1.58–5.41) were significantly associated with suicidal attempt. Conclusion. Suicidal ideation and attempt were high among HIV positive patients. Therefore early screening, treatment, and referral of suicidal patients are necessary in HIV clinics.