Background: Nowadays, peoples living with the Human Immunodeficiency Virus (HIV) were enrolled into lifelong Anti-Retroviral Treatment (ART) irrespective of their Cluster of Differentiation 4 (CD4) cell count as well as clinical disease staging. Though access to anti-retroviral therapy is rapidly expanding, ensuring long-term follow-up and retention on ART remains a threat to the success of ART program targets. This requires the identification of both the incidence and predictors of loss to follow-up following the Treat and Test strategy. However, studies in Ethiopia are lacking. Objective: To assess the incidence and predictors of loss to follow-up among adults receiving ART the following Test and Treat strategy at Felegehiwot Comprehensive Specialized Hospital (FHCSH), Northwest Ethiopia, 2021 Methods: Institution-based retrospective follow-up study was conducted on 513 Adults who had enrolled in ART from November 2016 to October 2020 at FHCSH, Northwest Ethiopia. Study participants were selected by computer-generated simple random sampling technique. Data was extracted from the charts of all eligible patients using a checklist adapted from ART intake and follow-up forms, entered to Epidata-version 3.1, and exported to Stata version 14.2 software for analysis. The Kaplan–Meier survival curve was used to estimate the loss to follow-up free survival probability. Variables with P-values ≤ 0.25 in the bivariable analysis were fitted into the multivariable cox regression model. Finally, variables with p-values < 0.05 in the multi-variable Cox regression analysis were considered as significant predictors of loss to follow-up. Result: - From a total of 513 sampled HIV-positive patient charts, 507 (98.8%) were included in the final analysis. Of those participants, 93 (18.3%) were lost to follow-up, yielding an Incidence rate of loss to follow-up 9.7 per 100 person-years of observation (95% CI: 7.9 -11.9). In the final model, rapid ART initiation (Adjusted Hazard Ratio(AHR):2.03, 95% CI:1.23- 3.33), not disclosing HIV-status (AHR:2.08, 95%CI:1.27-3.40), poor/ fair ART adherence (AHR:3.8, 95%CI:2.37-6.09), ambulatory functional status(AHR:1.77, 95%CI:1.10-2.82), and not receiving Cotrimoxazole preventive therapy (AHR:1.76, 95% CI: 1.14-3.2) were identified as significant predictors of time to loss to follow-up. Conclusion and recommendation- The incidence of loss to follow-up was relatively high with its highest figure observed in the first 06 months. Patients with rapid ART initiation, who didn’t disclose their status, had poor/fair drug adherence, had ambulatory functional status, and not receiving Cotrimoxazole preventive therapy were at higher hazard of loss to follow-up. Therefore, a universal test and treat strategy shall be provided cautiously, and due attention shall be given to those high-risk patients.