Background: Maternal mortality is relatively high in Ethiopia with more than one in five deaths to women aged 15-49 years. This is mainly attributed to pregnancy and pregnancy related causes. Postnatal care utilization is extremely low in Ethiopia with more than nine in ten mothers received no postnatal care at all while only 5% received postnatal care within the critical first two days after the delivery. Therefore, the objective of this study was to identify the magnitude and determinants of postnatal care services utilization in Hadiya Zone, Southern Ethiopia. Methods: A community based cross sectional quantitative study was conducted in Hadiya Zone of Southern Ethiopia during January and February 2009. A multi stage sampling technique was used to select the study participants from one urban and five rural kebeles. A total sample size of 710 was determined using single population proportion formula. The data was analyzed using SPSS version 16 statistical software. Logistic regression analysis was used to determine association between dependent and independent variables using both crude and adjusted odds ratio with 95% confidence interval. Result: More than seven in ten mothers received no postnatal care at all and only 22.7% received postnatal care within the critical first two days after delivery. Antenatal care attendance, place of delivery, and distance from the facility were major predictors of postnatal care service utilization. Besides, cultural belief, maternal workload, not knowing about postnatal care, and being apparently healthy were major reasons reported for not attending postnatal care. There is no marked variation of postnatal care utilization within the first two days of birth by the age of the mothers. Conclusion: Postnatal care uptake was low and predicted by reasonably modifiable factors such as antenatal care visit, place of delivery and physical accessibility of the health facilities. Therefore, improvement in the uptake of postnatal care could be expected provided that measures targeted at raising antenatal care visit and institutional delivery is introduced timely.