Background: Sore throat with mouth dryness is a public adverse consequence of upper gastrointestinal endoscopy several days after the procedure, which can negatively affect patients' comfort, swallowing, and oral nutrition. Aim: To evaluate the effect of warm saline solution gargling on patients' sore throat and mouth dryness post upper gastrointestinal endoscopy. Design: A quasi-experimental research design (study/control) was used. Sample: A purposive sample of 120 patients undergoing upper gastrointestinal endoscopy. Setting: This study was applied in the gastric endoscopic unit and the department of gastrointestinal and hepatic disorders at Minia University Hospital, Egypt. Methods: Three validated tools were utilized. 1) A structured interview questionnaire involved personal and medical profiles, 2) the Prince Henry pain scale, and 3) the Xerostomia Inventory (XI) scale. Results: The mean ages were 54.8±12.5 and 58.2±9.4 for the study and control groups respectively; 51.7% and 60% of both groups were males, respectively. The mean score of sore throat declined among the intervention group after gargling with warm normal saline solution at follow-up phases against the control group, with statistically significant differences (P-value =0.001**). Added to this, 48.3% and 41.7% of the study and control groups respectively, suffered from moderate mouth dryness at the pretest and then this ratio lessened to 20% and 11.7% for the intervention group after 24 hours and after two weeks respectively, versus 38.3% and 33.3 % for the control group respectively, with a statistically significant difference among the two groups. Conclusion and recommendations: Warm saline solution gargling is an effective and simple approach to alleviate sore throat and mouth dryness for both adults and elderly patients after upper gastrointestinal endoscopy. Hence, it is recommended to use this beneficial procedure as a routine part of care for all patients getting gastric endoscopy.