Little has been known about the magnitude and predictors of contraceptive use in extended postpartum period in Ethiopia. Thus, this study aims to assess the magnitude and determinants of contraception utilization in extended postpartum period. A community based cross-sectional survey was conducted in Gida Ayana district, Oromia regional state, Ethiopia in February 2015. Six hundred and three postpartum women were included using a multistage sampling technique. Descriptive statistics were used to summarize the data and logistic regressions were used to assess the predictors of modern family planning use at 95% confidence interval.The proportion of women using any of the modern family planning in extended postpartum period was 45.4%. Women who had four and more antenatal care visits (AOR = 2.93; 95% CI 1.08-7.94), mothers who received post-natal care (AOR = 4.34; 95% CI 2.37-7.94), and those desiring less number of children (AOR = 5; 95% CI 2.19-11.41) were more likely to use modern family planning methods during the extended postpartum period. Therefore, health care providers should work to improve quality of health services provided during antenatal care and postnatal care to enhance family planning utilization among post-partum women.