This study aims to determine and compare nursing students' and mechanical engineering students' codependency levels and the factors that affect codependency. This study is designed as a descriptive-comparative research. Data has been collected using an information form and the Codependency Assessment Tool (CODAT). Higher scores indicate higher levels of codependency. The sample consists of 283 undergraduate students who voluntarily participated in this study. The data has been evaluated in SPSS 11.5 using statistical tests such as frequency, mean, independent-samples t-test, and one-way ANOVA testing. Students' mean CODAT score was 51.89 (SD = 9.93). Students were found to have mild level codependency. No statistically significant difference was found to exist between total scale scores and gender, or between nursing students' and mechanical engineering students' total CODAT scores. However, mechanical engineering students had higher scores than nursing students for the hiding-self subscale. First-year students with a history of mental illness, being treated for mental illness, or current/previous alcohol or drug use who expressed having more familial problems have significantly higher scores. The results obtained from this study contribute to the literature on codependency in terms of the nature of and factors affecting codependency.