Background: Surgical treatment is the most effective method of treatment for obesity; and laparoscopic sleeve gastrectomy (LSG) is the most frequently performed bariatric surgery. Objective: The aim of the study was evaluation of the frequency of occurrence and the degree of progression of changes characteristic of GERD in patients who had undergone LSG in clinical; endoscopic; and microscopic images in the obtained bioptats; and an attempt to correlate the results obtained with the effectiveness of bariatric treatment. Materials and Method: The anonymized clinical data concerning 214 patients who had undergone LSG were collected from the database. Invitations for check-up examinations were distributed, to which 37 patients responded. Two patients were excluded from the study. In 35 patients after LSG check-up clinical examination, bariatric endoscopy (BE) and bariatric microscopy (BM) were performed on bioptats collected from the site of the gastro-esophageal junction; and 3 specimens collected at 2 cm intervals from the Z-line. The study was performed according to the standard protocol. Results: In the analyzed group, clinical symptoms of GERD occurred in 12 patients (34.5%), including 10 females and 2 males. The symptom reported by all patients was retrosternal pain/burning (heartburn). In BE, foci of ectopic mucosa in the epicardial part of the esophagus were found in 16 patients (14 F and 2 M). No correlation was observed between the analyzed parameters and the occurrence of the above-mentioned changes. In BM, only in three patients were the changes described as normal esophageal mucosa; while in another three, as foci of intestinal metaplasia, Barrett’s esophagus. In this group no foci of dysplasia were found. In eight patients, the changes were described as inflammatory. In ten patients from this group, microscopic changes occurred without clinical symptoms of the disease. Conclusions: GERD is an important clinical problem in patients after LSG; therefore; the problem of occurrence or exacerbation of symptoms of the disease should be discussed with the patient during qualification for bariatric surgery. The bariatric effectiveness of LSG does not correlate with the occurrence of the symptoms of GERD after the procedure. However; the lack of clinical symptoms of the disease does not mean the lack of its occurrence. Therefore; the endoscopic check-up after LSG should be routinely performed. During the qualification for LSG screening, histopathologic examinations of the esophagus may be useful for the assessment of the microscopic symptoms of GERD in oligosymptomatic patients; and exclusion of rare pathologies of the esophagus (e.g., eosinophilic esophagitis), which may complicate post-operative course.