For years, several surgical and non-surgical therapeutic strategies in Eustachian tube dysfunction have been described. The Endonasal dilatation of the Eustachian tube (EET) utilising a balloon catheter is a feasible option in patients with symptoms of chronic obstructive Eustachian tube dysfunction. However, long-term results in a large series are missing. In a prospective case series, 217 patients (342 cases) with symptoms of chronic Eustachian tube dysfunction underwent uni- or bilateral EET at the ENT Department of the University of Hamburg, Germany, between September 2010 and April 2013. A tube score consisting of the type of tympanogram and the R value of the tubomanometry was used to evaluate pre- and postoperative tube function. All patients underwent follow-up with a post-operative interval of 3-12 months. The mean value of the pre-treatment tube score was 2.23 ± 1.147 and significantly improved to 2.68 ± 1.011 1 year after EET. There was a significant increase in the tube score during follow-up. The co-variables time period, tympanoplasty and pressure range showed a significant impact on the tube score. EET is a minimally invasive and effective treatment of chronic obstructive tube dysfunction. It is a safe procedure without causing significant complications. Nevertheless, long-term results of larger, placebo-controlled multicentre studies are needed to confirm its effectiveness.