Background/Aims: The evidence suggests that a shorter esophageal length (EL) in gastroesophageal reflux disease (GERD) patients is associated with the presence of hiatal hernia (HH). However, there are no reports of this association in patients with achalasia. The aim is to (1) determine the prevalence of hiatal hernia in achalasia patients, (2) compare achalasia EL with GERD patients and healthy volunteers (HV), (3) measure achalasia manometric esophageal length to height (MELH) ratio, and (4) determine if there are differences in symptoms between patients with and without hiatal hernia. Methods: This retrospective and cross-sectional study consist of 87 pre-surgical achalasia patients, 22 GERD patients, and 30 HV. High-resolution manometry (HRM), barium swallow, and upper endoscopy were performed to diagnose HH. The EL and MELH ratio were measured by HRM. Symptoms were assessed with Eckardt, Eating Assessment Tool, and GERD–health-related quality of life questionnaires. Results: The HH in GERD’s prevalence was 73% vs 3% in achalasia patients (P < 0.001). Achalasia patients had a longer esophagus and a higher MELH ratio than HV and GERD patients (P < 0.001). GERD patients had a lower MELH ratio than HV (P < 0.05). EAT-10 (P < 0.0001) and Eckardt (P < 0.05) scores were higher in achalasia without HH vs HH. Conclusions The prevalence of HH in achalasia is significantly lower than in GERD. The longer EL and the higher MELH ratio in achalasia could explain the lower prevalence of HH. Despite the low prevalence of HH in achalasia patients, the surgeon should be encouraged not to rule out HH since the risk of postoperative reflux may increase if this condition is not identified and corrected.