Background: Early presentation for HIV care is vital as an initial tread in the UNAIDS 90-90-90 targets. However, late presentation for HIV care (LP) challenges achieving the targets. This study assessed the prevalence, trends, outcomes and risk factorsfor LP. Methods: A 12 year retrospective cohort study was conducted using electronic medical records extracted from an antiretroviral therapy (ART) clinic at Jimma University Teaching Hospital. LP for children refers to moderate or severe immune-suppression, or WHO clinical stage 3 or 4 at the time of first presentation to the ART clinics. LP for adults refers to CD4 lymphocyte count of < 200 cells/ μl and < 350 cells/μl irrespective of clinical staging, or WHO clinical stage 3 or 4 irrespective of CD4 count at the time of first presentation to the ART clinics. Binary logistic regression was used to identify factors that were associated with LP, and missing data were handled using multiple imputations. Results: Three hundred ninety-nine children and 4900 adults were enrolled in ART care between 2003 and 15. The prevalence of LP was 57% in children and 66.7% in adults with an overall prevalence of 65.5%, and the 10-year analysis of LP showed upward trends. 57% of dead children, 32% of discontinued children, and 97% of children with immunological failure were late presenters for HIV care. Similarly, 65% of dead adults, 65% of discontinued adults, and 79% of adults with immunological failure presented late for the care. Age between 25- < 50 years (AOR = 0.4,95% CI:0.3-0.6) and 50+ years (AOR = 0.4,95% CI:0.2-0.6), being female (AOR = 1.2, 95% CI: 1.03-1.5), having Tb/HIV co-infection (AOR = 1.6, 95% CI: 1.09-2.1), having no previous history of HIV testing (AOR = 1.2, 95% CI: 1.1-1.4), and HIV care enrollment period in 2012 and after (AOR = 0.8, 95% CI: 0.7-0.9) were the factors associated with LP for Adults. For children, none of the factors were associated with LP. Conclusions: The prevalence of LP was high in both adults and children. The majority of both children and adults who presented late for HIV care had died and developed immunological failure. Effective programs should be designed and implemented to tackle the gap in timely HIV care engagement.