Neonatal sepsis remains a leading cause of morbidity and mortality in neonates across all regions, including Africa. Compared to developed and some developing countries, there are relatively few epidemiological trends for neonatal sepsis and associated patterns with COVID-19 in Ethiopia. We modeled an epidemiological trend and pattern to aid in the monitoring of changes in neonatal sepsis. Retrospective data were collected from all admissions to the Neonatal Intensive Care Unit (NICU) in Ethiopia at Jimma Medical Center between May 2019 and April 2022. We analyzed the monthly neonatal sepsis incidence, mortality, and case-fatality rates using STATA software. Finally, we modeled a monthly time series of neonatal sepsis incidence trends and patterns associated with the COVID-19-impacted period using Joinpoint software. For all analyses, a P value of 0.05 was considered statistically significant at the 95% confidence interval (CI). In the 36 months, 6796 cases were admitted to the NICU, with a 9.5% (95% CI: 9.1, 10.0) incidence rate of neonatal sepsis. The overall admission mortality rate was 16.5% (95% CI: 13.6, 19.8), while sepsis-attributed mortality was 7.1% (95% CI: 5.8, 8.5). The data showed an unstable decreasing trend for three Joinpoints (August 2020, December 2020, and August 2021). Notably, a decrease in the incidence trend was observed from May 2019 to August 2020 (MPC, -4.1; 95% CI: -7.6, -0.5; P = 0.03), followed by a sharp increase (MPC, 23.7; 95% CI: -13.8, 77.7; P = 0.24) from August 2020 to December 2020. From December 2020 to August 2021, there was again a decreasing trend (MPC, -13.8; 95% CI: -23.3, -3.5; P = 0.01), followed by a slight increase from August 2021 to April 2022 (MPC, 4.2; 95% CI: -8.4, 18.6; P = 0.52). Finally, the study revealed an association between patterns of neonatal sepsis incidence trends and COVID-19, with a Joinpoint jump model comparability ratio (CR = 0.43) between pre- and COVID-19-impacted periods. Neonatal sepsis was prevalent at Jimma Medical Center, but it was on an unstably declining trend. The current results suggest a potential temporal association between the intensity of COVID-19 containment measures and a change in the incidence trend and patterns of neonatal sepsis. However, the quantified contribution of a particular containment measure requires further investigation.