Purpose: Proton pump inhibitors (PPIs) are commonly prescribed for laryngopharyngeal reflux (LPR), but their efficacy remains debated. Alginates is an option for the treatment of LPR with few adverse effects. The study aimed to investigate the non-inferiority of an alginate suspension (Gastrotuss^®) compared to PPIs (Omeprazole) in reducing LPR symptoms and signs. Methods: A non-inferiority randomized controlled trial was conducted. Fifty patients with laryngopharyngeal symptoms (Reflux Symptom Index -RSI- ≥ 13) and signs (Reflux Finding Score -RFS- ≥ 7) were randomized in two treatment groups: (A) Gastrotuss^® (20 ml, three daily doses) and, (B) Omeprazole (20 mg, once daily). The RSI and the RFS were assessed at baseline and after 2 months of treatment. Results: Groups had similar RSI and RFS scores at baseline. From pre- to 2-month posttreatment, the mean RSI significantly decreased (p = 0.001) in alginate and PPI group (p = 0.003). The difference between groups in the RSI change was not significant (95%CI: − 4.2–6.7, p = 0.639). The mean RFS significantly decreased in alginate (p = 0.006) and PPI groups (p = 0.006). The difference between groups in the mean change RFS was not significant (95%CI: − 0.8; 1.4, p = 0.608). Conclusion: After 2 months of treatment, LPR symptoms and signs are significantly reduced irrespective of the treatment. Alginate was non-inferior to PPIs and may represent an alternative treatment to PPIs for the treatment of LPR.