ABSTRACT Background: Seborrheic keratosis (SK) is one of the most common dermatologic lesions. Although SKs are benign, patients with SKs frequently desire treatment for symptoms of itching and irritation or for cosmetic purposes. Objective: to evaluate the treatment of SK using diclofenac sodium gel 3% confirmed dermoscopically before and after treatment. Methodology: This study was interventional randomized controlled single blinded clinical trial carried out on 60 SK patients; their ages ranged from 41-70 years old. Cases were selected from the outpatient dermatology clinic at Al-Zahra University Hospital at the period from January 2018 to May 2019. Patients were divided into 2 groups: group A (study group) included 30 patients who were submitted to diclofenac sodium gel 3% twice per day for 2 months and group B (control group) included 30 patients who were taking placebo in the form of Petroleum Jelly originally (Vaseline). Dermoscopic examination was done before and after treatment to confirm the diagnosis and evaluate the response. Results: in study group, complete clearance was detected in 13.3%, nearly clear in 53.4%, ≤ 1 mm thick in 23.3% and > 1 mm thick in 10.0%. As regard color, 43.3%showed no change in color (dark brown) and 56.7% cases changed to light brown, whilein control group none of our patients showed complete clearance, 13.3% showed nearly clearance, ≤ 1 mm thick in 30.0% and > 1 mm thick in 56.7%. Regarding color all cases were still dark brown. Conclusion: Diclofenac sodium gel 3% is an effective, non-invasive method of treating SK.