Background/Aims: Sigmoid esophagus and/or megaesophagus are considered as an advanced stage in the natural history of achalasia cardia. The role of peroral endoscopic myotomy (POEM) in these subset of patients is emerging. We performed a systematic review and metanalysis to study the efficacy of POEM in advanced achalasia cardia with sigmoid and megaesophagus. Methods: A literature search in PubMed and Embase was done from inception till August 3, 2021 to look for studies reporting exclusively on the role of POEM in advanced achalasia cardia with sigmoid and/or megaesophagus. The random effect method with inverse variance approach was used for the computation of pooled prevalence. For 2 groups’ analysis of continuous outcome standardized mean difference was used as the summary measure. Results: Eleven studies with 428 patients were included for analysis. The pooled technical and clinical success was 98.27% (95% CI, 96.19-99.22; I 2 = 0%) and 89.38% (95% CI, 84.49-92.86; I 2 = 26%) and on subgroup analysis into sigmoid and megaesophagus it was (98.06% [95% CI, 95.41-99.19; I 2 = 0%], 98.47% [95% CI, 92.72-99.69; I 2 = 0%] and 87.92% [95% CI, 80.68-92.70; I 2 = 37%], 88.36% [95% CI, 62.62-97.17; I 2 = 77%]) respectively. The clinical success at < 1 year and 1-3 year follow-up was 89.37% (95% CI, 82.82-93.61; I 2 = 0%) and 88.66% (95% CI, 81.65-91.22; I 2 = 46%) respectively. There was a significant reduction in the post-POEM scores with standardized mean difference for Eckardt score (4.81), for integrated relaxation pressure at 4 seconds (1.93), and for lower esophageal sphincter pressure (2.06). Conclusions POEM is an effective modality of treatment even in the subset of patients of advanced achalasia cardia with sigmoid and megae sophagus.