Purpose <p>Non-pharmacological complementary therapies in cancer treatment strengthen care. This study aims to investigate the effects of mandala activity on postoperative pain, anxiety level and analgesia use in gynaecological oncology patients.</p> Materials and methods <p>This study is a randomised controlled, two-group pretest/posttest comparative study. The study included 42 patients who underwent open abdominal hysterectomy at a training and research hospital in Istanbul between 1 February and 1 August 2023. Introductory Information Form, Visual Analog Scale (VAS), State-Trait Anxiety Inventory (STAI-I), Postoperative Patient Evaluation Form and Mandala Activity Booklet were used throughout the study.</p> Results <p>Preoperative State Trait Anxiety Inventory (STAI-I) score was significantly higher in the control group (63.48 ± 5.31) compared to the intervention group (56.33 ± 7.65) (<i>p</i> &lt; .05). Postoperatively, the STAI-I score of the control group decreased to 47.43 ± 8.29, while the intervention group showed a significant decrease to 31.52 ± 6.73. In addition, the Visual Analog Scale (VAS) scores of the control group decreased from 7.17 ± 1.42 preoperatively to 0.82 ± 1.46 postoperatively, while the intervention group scores decreased from 6.68 ± 2.11 to 1.77 ± 1.79, indicating that mandala activity was significant (<i>p</i> &lt; .05).</p> Conclusion <p>In conclusion, this study showed that postoperative mandala activity effectively reduced pain and anxiety levels and influenced the use of analgesia in gynecologic oncology patients.</p>