Background: Unintended pregnancy has direct relation with poor utilization of maternal health care services and also associated with unhealthy behaviors during pregnancy. Few studies have examined the association between unintended pregnancy and maternal health behaviors during pregnancy in developing countries including Ethiopia. The purpose of the study was to determine the association of unintended pregnancy with use of antenatal care during pregnancy among pregnant women in Hadiya zone, southern Ethiopia. Methods: Community based cross sectional study design was employed in Hadiya zone, southern Ethiopia in 2017. 748 pregnant mothers were included using single population proportion. Study participants were selected by simple random sampling technique. A structured interviewer administered questionnaire was used to collect data. Descriptive, bivariate and multivariate logistic regression was employed to identify the independent effect of unintended pregnancy on the outcomes of interest. The level of significance was confirmed if p-value was less than 0.05. Results: More than one third (36.2%) of women reported unintended pregnancy. Unintended pregnancy was significantly associated with use of antenatal care. Women with unintended pregnancy were 69% less likely to receive ANC (AOR=0.31, 95% CI; 0.21–0.46) and were four times more likely to have late ANC initiation (AOR=4.40, 95% CI; 1.70–11.40) during pregnancy as compared to counterparts. Conclusion: This study finding showed an association between unintended pregnancy and ANC use during pregnancy. Women with unintended pregnancy were less likely to use antenatal care and more likely to delay initiation of antenatal care. Longitudinal studies are recommended on relationship between unintended pregnancy and ANC use.