Background. Globally, undernutrition is responsible for at least 35% of deaths in children less than 5 years of age and estimated 6% of under-five deaths can be prevented by ensuring optimal complementary feeding especially the dietary diversity and meal frequency. In Ethiopia, 5% of children were fed according to minimum standards with respect to food diversity. Objective. To assess the level of knowledge and practice of mothers on dietary diversity practices and associated factors for children 6–23 months in Adea woreda. Methods. Community-based cross-sectional study was conducted. A sample of 730 mothers who have children in the age group of 6–23 months were selected using systematic sampling. Logistic regression model was fitted in order to identify factors associated with knowledge and practice of dietary diversity practice. Result. Of the total 700, 357 (51%) were knowledgeable on dietary diversity but 112 (16%) practiced appropriate dietary diversity practice for their 6–23-month-old children. Husbands' education (AOR = 2.79, 95% CI = (1.55, 5.00)), mothers' age, and marital status were significantly associated with knowledge of mothers. Mothers' age, husbands' education, marital status, and knowledge of mothers were significantly associated with mothers' dietary diversity for 6–23-month-old children. Conclusion. This study showed that approximately half of the mothers have good knowledge on minimum dietary diversity for children 6–23 months old and very low proportion of children 6–23 months old received diversified meal according to Infant and Young Child Feeding indicators. It was identified that different factors are responsible for this discrepancy.