Background: The study evaluated the prevalence & impact of sarcopenia in gastroesophageal cancer (GC) & lung cancer (LC) patients undergoing resection. Methods: An observational prospective study was conducted in department of surgical oncology, AIIMS, New Delhi. All patients aged under 65 years with resectable GC & LC were included. Skeletal muscle index (SMI) using cross-sectional CT images at the level of L3 & Hand grip strength (dynamometer) were used to assess sarcopenia. Random benign patients with CT images were used as control group. Patients were categorized into sarcopenic and non-sarcopenic and outcome parameters were compared. Results: In the study population (n = 66), GC & LC constituted 44 (66.67%) & 22(33.33%) respectively. Mean age was 53.4 years. The prevalence of sarcopenia based on the combined method (CT imaging & handgrip strength) was 57.58%, CT based sarcopenia was 33.34% & handgrip strength-based sarcopenia was 43.93%. Mild and moderate sarcopenia was seen in 37.88% (n = 25) & 19.7 % (n = 13) respectively. Among patients with GC, prevalence of sarcopenia was 59.09% by combined method, 36.36% and 43.18% by CT based method alone & handgrip strength-based method alone respectively. Among LC prevalence of sarcopenia was 54.54% by combined method, 27.27% and 45.45% by CT based & handgrip-based method. The concordance between CT muscle mass & grip strength was 62.12%. Most female patients had weak handgrip strength despite having normal SMI. In control group (n = 44) mean age was 54.5 years, the prevalence of CT based sarcopenia was 34.09%. Weight loss history & BMI correlated with the degree of sarcopenia. Out of 66 patients 13% (n = 9) patients were unresectable. Moderate sarcopenia group had more statistically significant (P -0.02) unresectable disease compared to mild and non-sarcopenic groups. In postoperative period, sarcopenic group (64.51% vs 38.36 %) had more grade 2 complications though statistically insignificant. There was no difference in hospital stay between the two groups. In patients with GC , postoperative respiratory complication occurred in 11.53% (n = 3) of sarcopenic patients and 5.5%(n = 1) of non-sarcopenic patients, anastomotic leak occurred in 7.69% (n = 2) of sarcopenic patients and 5.5% (n = 1) of nonsarcopenic patients. Conclusions: The prevalence of sarcopenia is higher in patients with gastroesophageal cancer compared to lung cancer. The important factors that affect the sarcopenia include age and body mass index and weight loss history. The study has showed a trend towards increased post-operative complications and increased unresectable cases in patients with mild to moderate sarcopenia. Further larger studies are required to validate if sarcopenia can be used as an adjunct to predict resectability and post-operative outcomes.