Background and purpose: Intravenous (IV) catheterization is one of the common painful procedures in children. This study aimed to investigate the effect of cold and warm vibration on pain caused by IV catheterization in 3-to 6-year-old children using a buzzy device. Materials and methods: A randomized clinical trial was carried out in 108 children in Mashhad Akbar Pediatric Hospital selected via random blocking. They were divided into three groups to receive warm vibration, cold vibration, or vibration only (control group). In this study, a musical vibrating device in a form of bee with either a warm or cold pack was attached for 5 min at approximately 5-10 cm above the intravenous continuous infusion (IVCI) site. In last minute, vibration was applied, then, IV catheterization was done. The Wong-Baker FACES Pain Rating Scale (WBS) was used to rate pain severity. Data were analyzed in SPSS V19 at a significance level of 95%. Results: Before the intervention, there were no significant differences in mean pain score between the three groups (P>0. 05). Pain score was significantly different during the procedure (P<0. 05). Significant difference was seen in pain score between the two intervention groups (P<0. 05). The pain score was found to be significantly different between the intervention group that received cold vibration and the control group (P<0. 05), but, the score was not significantly different between the group with warm vibration and the control group (P>0. 05). Conclusion: Both cold and warm vibrations could reduce the pain caused by injection, but cold vibration showed greater effect on reducing pain. Therefore, cold or warm vibrating devices are suggested in management of aggressive painful procedures in children.