Background and objective: Oral mucositis is caused by the destruction of the oral mucosal epithelium and suppression of its growth secondary to antineoplastic treatment in the form of chemotherapeutic drugs, substances, or radiotherapy. This study aimed to evaluate oral mucositis in pediatric cancer patients because it is one of the common side effects of cancer therapy that influences the outcome. Methods: This is a cross-sectional study that enrolled 100 pediatric patients with both hematological and non-hematological cancer. The age of the patients ranged from 1-18 years, involving both genders. Cases admitted to Hiwa hospital were clinically evaluated for oral mucositis, and ethical permission was taken from parents. Risk factors were assessed, including age, sex, cancer type, type of chemotherapy, radiotherapy, number of cycles, complete blood count, interleukin-1 beta, interleukin-6, tumor necrosis factor-alpha, and tumor necrosis factor-beta. Results: Baseline serum cytokines levels showed significant correlation between Interleukin-6 and intensity of the oral mucositis (P = 0.003, rho = 0.314) and no correlation between severity of oral mucositis with tumor necrosis factor-alpha, tumor necrosis factor-beta nor interleukin-1 beta (P = 0.140 and rho = 0.258, P = 0.463 and rho = -0.079, and P = 0.706 and rho = -0.041, respectively). There was significant relationship between Hemoglobin level, neutropenia and type of non-hematological cancer with the intensity of oral mucositis respectively (P ≤0.001 and rho = -0.352, P = 0.027 and rho = -0.221, and P = 0.035 and rho = 0.095, respectively). Correlation between age, gender, white blood cell count, platelet count, type of hematological malignancy and past history with the intensity of the oral mucositis did not show significant result. Conclusion: Intensity of oral mucositis increased with anemia, neutropenia, high interleukin-6 level, and the type of non-hematological cancer. It is recommended to treat anemic, neutropenic patients as soon as possible before exacerbating the mucositis. Methotrexate is the most aggressive drug alone and in combined chemotherapy agents, which may cause mucositis and needs prophylaxis like topical nystatin suspension or other methods. Keywords: Oral mucositis; Pediatric cancer; Non-hematological; Hematological; Sulaymaniyah.