The aim of this study was to explore factors related to orthodontist’s decision making in providing orthodontic treatment for cleft Lip and palate patients in Thai public hospitals. The cross-sectional descriptive survey was conducted by online self-assessment. Chi-square and Kruskal-Wallis tests were used to compare between 3 groups which consisted of orthodontists who decided to treat cleft patients in all age groups (n = 60), treated patients in some age groups (n=24) and refused to treat cleft patients (n = 14). Factors which were statistical different between 3 groups consisted of background knowledge received from orthodontic training program (p = 0.033), hospital size (p < 0.01), number of dentists in their hospital (p < 0.01), present of cleft team (p < 0.01), had 2 or more orthodontists in their hospital (p < 0.01), well-coordinated cleft team (p < 0.01), and availability of hospital equipment (p < 0.01). In the group of orthodontists who decided to treat cleft patients, 85.0% of them worked in hospitals with a capacity of 200 beds or larger with an average of 18.17 dentists. In the group of orthodontists who did not treat cleft patients, 14.3% worked in hospitals with a capacity of 200 beds or larger with an average of 6.36 dentists. There was no statistical difference found in gender, age, experience, workload, and attitude. In conclusion, background knowledge received from their training program and several environmental factors consist of hospitals size, number of dentists, and present of well-coordinated staff in multidisciplinary team related to orthodontist’s decision making in providing treatment for cleft Lip and palate patients.