Objective: Assess knowledges and practices status on nutrition of mothers with children under 5 years old in Phu Thinh commune, Yen Son districts, Tuyen Quang province, 2011. Method: Cross-section study was using of 280 mothers with children under 5 years old. Results: The proportion of mothers have good knowleges on the food rich in nutrients (Tell 4 food stuff group named 15.1 percent and the food rich in Vitamin A was 23.6 percent). The proportion of mothers have good knowleges on the time exclusive breast feeding during 6 months (28.9 percent) and the time for stop breast feeding (13.6 percent). The rate of mothers find out the child have got early manorished was 26.7 percent, sign for early manorished children was 20.1 percent and the mothers know the way to care their children when they got diarrhea and acute respiratory (29.7 percent and 21.6 percent respectively). Conclusion: The knowledge and practices on nutrition of mothers with children under 5 years old have limitation. These findings may provide basic data for develop effective nutrition interventions in mountainous area.