Objective <p>We aimed to determine the diagnostic yield of bidirectional endoscopy in patients with iron deficiency anemia (IDA) by analyzing patients admitted to our clinic to investigate the etiology of IDA and those who underwent esophagogastroduodenoscopy (EGD) and colonoscopy.</p> Methods <p>Patients who underwent upper and/or lower gastrointestinal (GI) endoscopy procedures to investigate the IDA etiology in our hospital between May 2020 and November 2023 were included. Demographics, EGD and colonoscopic intervention reports, and pathological findings of all endoscopic procedures were analyzed.</p> Results <p>A total of 314 patients were analyzed. One hundred and fifty patients (47.8%) were male and 164 (52.2%) were female, and the median age was 63 (17–90) years for male patients and 57 (22–87) years for female patients. Bidirectional GI endoscopy was performed in the same session in 281 patients (89.5%), colonoscopy in 13 patients (4.1%), and EGD in 20 patients (6.4%). While our rate of detecting the cause of IDA was 10.5% in patients who underwent EGD or colonoscopy as a single procedure, it was 89.5% in patients who underwent bidirectional GI endoscopy.</p> Conclusion <p>Bidirectional gastrointestinal endoscopy may be considered a valuable approach for identifying the etiology of iron deficiency anemia in adult patients, regardless of age and sex, particularly in appropriate clinical contexts.</p>