Abstract Background High resolution manometry (HRM) has been proven able to describe the pathophysiological pathway leading to gastroesophageal reflux disease (GERD). Recently, a new manometric tool, the Milan Score (MS), has been introduced and validated to evaluate the risk of pathologic GERD, defined as Acid Exposure Time (AET) >6% at pH-study. Aim of this study is to validate this score in the post-operative assessment after laparoscopic antireflux surgery (LARS). Methods All patients who underwent HRM after LARS between October 2020 and May 2023 were included. The MS was calculated assessing four manometric variables: esophagogastric junction (EGJ) type, EGJ contractile integral (EGJ-CI), ineffective esophageal motility (IEM) and response to the straight leg raise (SLR) manoeuvre. The MS was considered pathologic if ≥137 (risk of GERD ≥50%). The risk of GERD was categorized into six classes, according to the MS score. The MS was compared with validated questionnaires for reflux symptoms, including GERD Questionnaire (GERD-Q), GERD Health-Related Quality of Life (GERD-HRQL) and Reflux Symptom Index (RSI), and with postoperative endoscopy findings. Results A total of 160 patients were included (63% males, age: 53 years, time from surgery: 30 months). Surgical techniques included magnetic sphincter augmentation in 54% of patients, Toupet fundoplication in 29% and Nissen or Dor fundoplication in 17%. The proportion of patients with MS ≥137 among those with pathologic questionnaires was 73% for GERD-Q (p<0.001), 75% for GERD-HRQL (p<0.001) and 78% for RSI (p<0.001). The rate of pathologic questionnaires increased for higher MSs. A MS ≥137 was related to recurrent hiatal hernia (23%, p=0.046) and esophagitis (21%, p=0.007) at endoscopy. Clinical and manometric outcomes were similar among different surgical techniques. Conclusions The MS is an efficient tool to assess the efficacy of LARS. Various surgical techniques have similar distribution in the different risk classes for GERD identified by MS, and similar clinical results. HRM with MS represent an easy and feasible assessment of surgical outcomes after LARS, providing an objective evaluation of the antireflux barrier after surgery.