Aim: Functional abdominal pain disorders (FAPDs) and functional constipation (FC) are the common functional gastrointestinal disorders in adolescents. We aimed to determine the prevalence of FAPDs and FC in adolescents using the Rome IV Questionnaire of Pediatric Gastrointestinal Symptoms and the factors associated with these two functional gastrointestinal disorders. Methods: A survey for the prevalence of FAPDs and FC in adolescents was carried out at two high schools. A translated and validated Thai version of Rome IV Questionnaire of Pediatric Gastrointestinal Symptoms was used. Potential associated factors were also collected. Psychosocial problems were evaluated by using the Strengths and Difficulties Questionnaire. Results: A total of 1700 adolescents (55.5% females) with a mean age (SD) of 16.1 (0.9) years were enrolled. The prevalence of FAPDs and FC was 5.3% and 8.1%, respectively. The subtypes of FAPDs were functional dyspepsia (4.7%; postprandial distress syndrome 3.9% and epigastric pain syndrome 0.8%), irritable bowel syndrome (0.6%), abdominal migraine (0.4%) and functional abdominal pain not otherwise specified (0.3%). Multiple logistic regression analysis revealed that FAPDs were associated with female gender (odds ratio (OR) 3.3, 95% confidence interval (CI): 1.7-6.4), underlying allergic diseases (OR 3.2, 95% CI: 1.6-6.6) and concomitant emotional problem (OR 2.7, 95% CI: 1.2-5.9). No significant associated factors with FC were found. Conclusion: FAPDs and FC are common in adolescents. Postprandial distress syndrome is the most common subtype of FAPD. Associated factors for FAPDs may suggest hormonal, immune-related and psychological involvement in the disease pathogenesis.