BACKGROUND:In Ethiopia, maternal health service utilization is very low,especially postnatal care (PNC). The percentage of mothers who receive care within two days of childbirth has shown little progress, from 2.4% in 2000 to 13% in 2014. However, it is very far below the expected level as compared to other sub-Saharan regions. Therefore, the aim of this study was to assess PNC services utilization and its associated factors among married women in Benchi-Maji Zone, Southwest EthiopiaMETHOD:Across-sectional studywas conducted from June 15 to August 15, 2015. A total of 801 married women wassampled from randomly selected districts in the zone.Semi-structured questionnaire was used to collect, data and informed consent was obtained from participants. The collected data were entered into the computer using Epi-data version 3.0, and then exported to SPSS Windows version 20.0 for analysis. Logistic regression was used to identify important predictors of PNC utilization.RESULT:Out of 765 participants, 392(51.24%) of married women who attended PNC in this study. Out of them, more than two-third 305(77.8%) attended mainly toimmunize their baby.The vast majority, 251(86.3%), of respondents mentioned lack of information as a main reason for not following PNC, and of them, the majority mentioned that they were appointed to come after 45 days for Family Planning(FP). In comparison with house wives, farmer women were less likely (AOR 0.3, 95 % CI 0.2-0.7) to attend for PNC. Awareness of problems during postnatal period showedthe strongest association in which those who knew the problems were about nine times (AOR 8.7 95 % CI 5.6-13.4) more likely to attend PNC. Similarly, married women who followedantenatal care (ANC) were more likely (AOR 2.2 95 % CI 1.1-4.6) to attend PNC in comparison with those who did not attend ANC at all.CONCLUSION: Residence, ANC follow-up, maternal occupation, awareness about problems of postnatal period had effects on use of PNC. In light of this study, providing deep counselling about PNC at the timeof ANC visit and discharge after delivery is strongly recommended. Furthermore, targeting more of rural married women may increase PNC utilization.KEYWORDS: PNC, Benchi-Maji, Southwest Ethiopia, Cross-sectional study, Mizan-Tepi University