Introduction: Institutional delivery is very low in Ethiopia, particularly in Oromia where less than one-third of antenatal care attendees utilize the services. This study assessed the magnitude of institutional delivery and associated factors in South West Showa Zone of Oromia.

Methods: A cross-sectional community based study was conducted in 2010. A stratified cluster sampling technique used to select study districts, villages and households. Four hundred thirty childbearing women with at least one birth in the past 5 years preceding the survey were interviewed. Qualitative study method was employed to supplement the quantitative data. Data analyses were done using SPSS v15. Frequency tables and percentages were used to describe study population. Association of independent variables with outcome variable was measured using odds ratio with 95% confidence interval. Multivariate logistic regression analysis was run to control for confounding variables.

Results: Eighty percent (344) respondents were from rural. Mean age of the women was 28.8 (±6.6). Most (70.5%) respondents and 39% of their husbands were uneducated. A quarter of them delivered at health institutions over five years preceding the survey. In a regression model with maternal age, residence, maternal and paternal education, all were significantly associated with use of institutional delivery services. Obstetric factors have also showed a statistically significant association. The qualitative findings revealed that trust in traditional birth attendants and health workers’ negative attitude were among the reasons for not delivering at health institutions.

Conclusion: Institutional delivery service utilization in the zone is affected by maternal and paternal education, ANC attendance and duration of labor. Traditional beliefs and health workers’ negative attitude were among the identified barriers. Multiple interventions involving community, service providers and health system are recommended.