Background: : Thalassemia is an inherited blood disorder in which the body makes an abnormal form of hemoglobin that causes bone disorders including bone in the skull face and jaws It also affects alignment, causing abnormal bite, which can lead to tooth decay, gingivitis and even inflammation of gums. Objective:: the aim of this study was to study the oral health of children 6 to 12 years of age with Thalassemia at the Child Hospital, Vientiane Capital. Methodology: : This was a cross-sectional study using a quantitative model to describe factors related to oral health in children with Thalassemia aged 6 to12 years that were treated at the Child Hospital. The study population was children with Thalassemia, and the totals of samples size were 375 children. Data was collected through face-to-face interviews on their socio–demographic characteristics, medical information and parental knowledge of oral behavior in oral health care for children. The information was entered into Epi data program version3.1 and using STATA program version 13. Frequency distribution was used to describe the data in percentage, means, averages and standard deviation. Bi-variable analyses were made to measure the associations with Multiple Logistic Regressions, OR at 95% CI and P-value <0.05. Result:: The result of study showed that above half of children were females (55.5%) and 63.7% were aged between 6 to 8 years. Thalassemia affected the oral health 86.9% who permanent teeth and 92.8% with milk teeth. The factors associated with child oral health that were statistically significant were the 9 to 12 age group (OR = 0.12; 95% CI: 0.05 - 0.25, P = <0.001), parents' behavior regarding oral health care for children (OR = 2.66; 95% CI: 1.28 - 5.52, P = <0.008) and parental behavior regarding child care (seeing dentist) (OR =0.45; 95% CI: 0.23 - 0.89, P=<0.001). Conclusion: The proportion of children 6 to 12 years of age with thalassemia and poor oral health was high among both those with permanent teeth and those with milk teeth. That shows the importance of making plans for oral health care and oral health prevention for children admitted the Hospital.