Background Internet addiction is a condition that affects cognitive function, which has a detrimental impact on students' academic performance and increases their risk of experiencing psychological crises including anxiety and sadness.Objectives Examining the prevalence of internet addiction and its contributing factors among regular undergraduate students at Jimma University in South West Ethiopia was the primary goal of this study.Methods An institutional-based cross-sectional study design using a multistage random sampling technique among 772 students was conducted. We collected the data using pretested and structured questionnaires with self-administered techniques. We measured internet addiction with the Young Internet Addiction Test (YIAT). Epi Data Manager version 4.6 was used to enter data, which was then exported to SPSS version 25 for analysis. Descriptive statistics, bivariable and multivariable logistic regression models were used to analyze possible confounders, and variables at p-value less than 0.05 were declared as independent predictors of internet addiction.Result The prevalence of internet addiction among Jimma University, regular undergraduate students was 53.6%, (95% Confidence Interval (CI); (49.99%, 57.15%). Being dissatisfied with major study (AOR: 4.827, 95% CI = 2.029–11.484) and having a cumulative grade point average of promoted grade report (AOR|): 2.119, 95% CI = 1.321–3.397 Using the internet for entertainment (AOR: 1.558, 95% CI = 1.113–2.180), using the internet for Face Book (AOR: 2.780, 95% CI = 1.471–5.253), using the internet for telegram (AOR: 2.197, 95% CI = 1.434–3.365), depression (AOR: 2.061, 95% CI = 1.463–2.903), social anxiety (AOR: 4.565, 95% CI = 1.254–16.610) and poor social support (AOR: 2.132, 95% CI = 1.358–3.346) had significant associations with internet addiction.Conclusion This study revealed a comparatively high frequency of internet addiction among Jimma University students. Internet dependance was found to be associated with promoted grade reports, poor satisfaction with major studies, using the internet for entertainment, Facebook and Telegram, depression, social anxiety, and poor social support. As a result, integrating the efforts of stakeholders, including the ministry of education and universities, on the identified factors and raising awareness among university students would be a beneficial step toward reducing this high prevalence.