Introduction: There are more and more studies that demonstrate the anti-inflammatory effects of the traditional Mediterranean diet (TMD). The aim of the study was to assess the effects of an intervention with the TMD in patients with recurrent acute and chronic rhinosinusitis. Material and Methods: We performed a pretest–posttest comparison study in 114 patients (56 girls and 58 boys) aged one to five years who had three or more acute rhinosinusitis episodes in the period of 1 year. They were included for a year in the nutritional program “Learning to eat from the Mediterranean”. The anthropometric, clinical, and therapeutic characteristics were studied. Results: All the studied indicators showed a positive and statistically significant evolution. Of the patients, 53.5% did not have any episode of acute rhinosinusitis, and 26.3% had only one, compared to the 3.37 they had on average in the previous year. The use of antibiotics decreased by 87.6%. The degree of satisfaction of the families was very high. The Mediterranean Diet Quality Index (KIDMED) that assesses the quality of the TMD rose from 7.7 to 11 points. Conclusions: The adoption of the TMD could have promising effects in the prevention and treatment of recurrent acute and chronic rhinosinusitis, limiting the pharmacological and surgical intervention in many of these patients.