OBJECTIVE : Chemotherapy-induced phlebitis (CIP) is one of the most important and common complications in patients with cancer. Currently, the use of complementary methods to prevent or alleviate phlebitis symptoms has attracted great attention. In this study, we aimed to assess the effects of topical sesame oil in reducing the pain severity of CIP. METHODS : This randomized clinical trial was conducted on 60 patients with colorectal cancer afflicted with CIP. Patients received, twice a day for seven consecutive days, a 5-min massage solely (as the control group) or with 10 drops of sesame oil (as the experimental group) within the 10 cm radius of the affected site. The pain severity was evaluated by the visual analog scale on the first, third, fifth, and seventh days of the intervention. RESULTS : Mean changes of the pain severity compared to the baseline were significant on the third (P = 0.009), fifth (P < 0.001), and seventh (P < 0.001) days of the intervention in favor of the experimental group. Also, a significant reduction in the pain severity both in the experimental and control groups was observed during the seven days (F = 720.66, Ptime < 0.001); however, the decrease was more significant in the experimental group (F = 21.46, Pgroup < 0.001). CONCLUSIONS : Application of massage with sesame oil as a complementary method is effective in reducing the pain severity of patients with CIP.