Background: About 85% of the world's children under one year of age have received life-saving vaccines. An estimated 1.7 million children died in 2008 from vaccine-preventable diseases and in 2011, only 24% of the children were fully vaccinated. Objectives: To assess fully vaccination coverage and associated factors among children aged 12–23 months in Mecha district. Methods: A cross-sectional community-based study was conducted in 8 rural and 1 urban kebeles from April to October, 2013. A systematic sampling method was used for sample selection. Data were collected on 497 children aged 12–23 months from 497 representative households were collected using trained nurses. The data collectors assessed collected the vaccination status of the children based on vaccination cards or mother’s verbal reports using a pre-tested semi-structured interviewer administered questionnaire through house-to-house visits. Data were coded and entered into SPSS 20.0 versions. Bivariate and multivariate logistic regression analyses were used to assess factors associated with vaccination status of children.Those predictor variables with p-value < 0.05 were considered significantly associated with the outcome variable. Results: About 49.3 % of children aged 12–23 months were fully vaccinated by card and mother’s recall, and 1.6% children were not started vaccination. Using multivariate logistic regression models, factors significantly associated with fully vaccination were urban residence (AOR :2.401, 95% CI:1.011,5.705), mothers who have good knowledge on vaccination (AOR: 2.131, 95% CI:1.076, 4.217), taking the child to health institution during illness in the first year of life (AOR: 2.147 , 95% CI: 1.275, 3.615) ,institutional delivery (AOR :1.593 , 95% CI :1.037,2.445) and complete primary & above education of father of the child( AOR:1.814, 95% CI:1.008,3.265). Conclusion and recommendation: Complete vaccination coverage among children aged 12–23 months remains very low in the district. Health institution delivery , urban residence, mother's knowledge on vaccination and father complete primary and above level of education were found to be independent factors for fully child vaccination status of children in the district. Therefore both HEWs and other staff members of health centres should be improve awareness of the people by designing proper health education targeting the mother on vaccination.