Background: Optimal infant and young child feeding (IYCF) practices during the first 2 years of life is paramount importance as this period is the “critical window” for the promotion of health, good growth, behavioral and cognitive development. As per the WHO (2010) definition optimal IYCF is initiation of breastfeeding within 1 hour of birth; EBF for first 6 months of life, introduction of complementary food from locally available food and hygienically prepared around 6 months, increased breastfeeding during illness and recovery and also continued breastfeeding for up to 2 years of age. The aim of this study was to determine the magnitude and the practices of IYCF at North Achefer Woreda. Methods: Community based cross-sectional study design was conducted in North Achefer woreda, Amhara Region, Ethiopia from February 16 to 30, 2019. Multistage sampling technique was employed to select study participants. From four kebeles of the woreda data was collected using pre tested questionnaire at Denbola kebele adopted from WHO, EDHS survey questioner and prior similar studies done in other places. The data was entered and analyzed using SPSS ver. 25.0. P-value < 0.05 was considered significant. Result: A total of 588 of mothers of children 0-23 month‟s age were included in the study yielding response rate of 97.2%. The mean (±SD) age of mothers was 27.1 years (±4.9), ranges from 18 to 43 years. The magnitude of timely initiation of (within an hour) and EBF was 78.9% and 83.0%. Eight in ten (79.9%) of mothers and around one-eighth (13.4%) of them gave colostrum and pre lacteal food to their infants after birth respectively. The magnitude of appropriate CF was 43.9% while that of optimal IYCF practice among 0-23 months children was 43.4%. The multivariable analysis showed attending secondary [AOR, 3.5, 95%CI: 1.1, 13.0] and higher education [AOR :2.2, 95%CI: 1.1, 7.0], being merchant [AOR: 2.3, 95%CI: 1.1,4.9], family income of 3000-3999 ETB [AOR: 1.4, 95%CI: 1.2,3.0], health institution delivery [AOR: 1.4, 95%CI: 1.2,2.8], PNC utilization [AOR: 1.6, 95%CI: 1.0, 2.1], good knowledge [AOR: 3.6, 95%CI: 1.5,8.2] and favorable attitude [AOR: 1.2, 95%CI: 1.1, 1.9] were statistically significant predictors of optimal IYCF practice. Conclusion and recommendation: Sub optimal IYCF practice was prevalent and showing a gap compared to the WHO recommendation. Hence, there is a need to develop health education intervention targeting behavioral change in the study area regarding IYCF.