Background: ‘Loss of follow-up’ is a significant public health concern globally. Retention in preventive care among at-risk key and priority population groups is critical for the successful prevention of Human immune virus acquisition. Loss to follow-up of individuals has countless negative impacts on Human immune virus prevention outcomes. There is, however, limited information about the incidence and predictors of loss to follow-up in the study area. Thus, this study aimed to determine the incidence rate and predictors of loss to follow-up among pre-exposure prophylaxis users. Methods: A retrospective cohort study was undertaken using 240 pre-exposure prophylaxis users between May 2020, and May 26, 2022, at Addis Ababa selected health centers. All eligible clients who fulfilled the inclusion criteria were included in the study. Results and Discussion: A total of 240 participants with a median age of 32.0 years (interquartile range [IQR]: 27.0 to 40.0) had a median time since initiation of pre-exposure prophylaxis 21.2 months (IQR: 6.5 to 22.1). Almost half 122 (50.8%) were married, Being male is associated with 1.77 times in risk of getting lost than female (ARR=1.77, 95% CI =1.12-2.79).those who had no adherence counseling were associated with 1.86 times in the chance of  LTFU as compared to those who had have adherence counseling (ARR=1.863, 95% CI =1.184, 2.930, P-value=0.003). 86 (35.8%) experienced loss to follow-up and the overall incidence rate of loss to follow-up was 7.3 (95% CI: 4.3-12.6) per 100 person-years of observation (PYs).PrEP adherence strategies should  developed and designed as a holistic approach, acknowledging the contextual factors of key population groups. Conclusions: About 35.8% of clients became lost follow-up of pre-exposure prophylaxis users. the overall incidence of 7.3(4.3-12.6) per year of observation. Research preparedness involving key and priority population groups should be strengthened for Human immune virus prevention intervention evaluations in Ethiopia.