BACKGROUND: Bloating is a common gastrointestinal complaint which is difficult to treat. OBJECTIVE: This study investigated the efficacy and compliance of a formulation called KAASER comprised of Trachyspermum ammi (L.) Sprague seed, Zingiber officinale Roscoe. rhizome and Piper nigrum L. berry in the treatment of functional bloating. DESIGN, SETTING, PARTICIPANTS AND INTERVENTION: A total of 106 patients with functional bloating, between 20 and 50 years of age, participated in this double-blind randomized controlled trial. Patients were divided into 3 parallel groups that received 500 mg of placebo, dimethicone or KAASER, three times a day for 2 weeks. MAIN OUTCOME MEASURES: The frequency and severity of bloating were primary outcomes, while the frequencies of eructation, defecation, borborygmus and early satiation were secondary outcomes. All parameters were evaluated at the beginning (week 0), and also weeks 2, 4 and 10 of the study, through self-report checklists with a scoring system. RESULTS: Among the 84 patients who completed the study, the frequency and severity of bloating (P < 0.001), the frequencies of eructation, defecation and borborygmus (P = 0.03) were significantly improved in the group receiving KAASER (36 patients) compared with the dimethicone (35 patients) and placebo (35 patients) groups, during the 3 phases of follow-up. These significant differences persisted through the 2 and 8 weeks of follow-ups after cessation of medication (week 4 and 10). In early satiation, no significant differences were observed among the 3 groups. CONCLUSION: The results showed that KAASER can be effectively used to treat patients suffering from bloating. Bloating, eructation, defecation and borborygmus in the KAASER group remained significantly improved after 2 and 8 weeks of cessation of medication, making this mechanism an interesting area for further investigation. TRIAL REGISTRATION Registration trial IRCT2015100324327N on Iranian Registry of Clinical Trials.