Background: Substance use among Ethiopian adolescents is considerably rising; particular in college and university students. However, the magnitude of substance use and the factors associated with it has not been well investigated in the country. The main purpose of this study was to identify substance use prevalence among MaddaWalabu University undergraduate Students. Methods: A cross sectional study design was employed using self-administered structured questionnaires. Data were collected from a sample of 605 undergraduate students in the University. The data were analyzed using SPSS version 20. Descriptive and Inferential statistics were used for data presentation. Determinant factors for substance use were checked for significance association using Chi Square, One way ANOVA and Logistic regression with significance level set at p < 0.05. Results: The findings of this study shows that sociodemographic variables were determinant factors for substance use of the study participants. Among students who were ever users of one of the substances: tobacco, alcohol, cannabis, sedatives or Khat; it was seen that females are close to males in the use of these substances. There is statistically significant difference in age group (χ 2 = 9.69, df = 3, p<0.05). Compared to the final year students, second year students were 4 times more likely to have used one of the substances and first year students were also at high odds of being a substance user (2.6, AOR). Conclusion: Compared the second year students, first year students were at significant risk of ever using any one of the substances. This trend is alarming. Tobacco consumption or Khat use has been significantly associated with socio-demographic variables. Use of opiates were also reported. Hence it is important to carry out educational campaigns about addiction and its prevention.