Abstract Introduction: In cancer patients, the reduced food intake causes weight loss and promotes protein-calorie malnutrition. This results in loss of lean body mass, which affects both skeletal muscles and respiratory muscles. Objective: Evaluate and compare the respiratory muscle strength of patients with esophageal and stomach neoplasia during the preoperative period. Methods: This is a cross-sectional study carried out with 24 patients of both genders hospitalized in a teaching hospital. They underwent a physical therapy evaluation composed of anthropometric data and measurement of respiratory muscle strength through manovacuometry. Paired and unpaired t-tests were used to compare the values obtained with the predicted equations. Results: Regarding the disease prevalence, 66.66%(16) of the individuals had stomach neoplasm and 33.33%(8) esophageal neoplasm. Of the patients with esophageal neoplasm, 100% were men with a mean age of 63 ± 9.16 years. Of those with stomach neoplasm, 68.75% were men with a mean age of 69.36 ± 10.92 years. Female patients with stomach neoplasm had significantly higher BMI (p = 0.01) than male patients, and they were classified as overweight. Both neoplasms had significantly lower real values (p ≤ 0.05) than predicted values at the maximal expiratory pressure. Conclusion: Patients with esophageal and stomach neoplasms in the preoperative period present reduction in the expiratory muscle strength. There were no statistically significant differences, when we compared the maximum respiratory pressures between the two types of neoplasms investigated.