Background: Repair of cleft lip deformities requires careful planning to create functional and aesthetically pleasing upper lip contour. Cleft lip scar has a serious impact on appearance. Many factors affect the formation of a scar, as continuous muscle contraction.Methods: In this study, 22 patients with complete unilateral cleft lip were divided into two groups, the first group was injected with botulinum toxin (11 patients) and the other group control (11 patients) was injected with saline. Twenty patients completed the follow up, while the other two patients failed to commit to our follow up schedule. Injection was done with insulin syringe 7 days before primary lip repair using modified Millard cheiloplasty.Results: The BTX-A was statically insignificant in the philtrum length difference in cleft and non-cleft sides at one week. However the philtrum length difference as well as the scar width were statically significant less in BTX-A than the control in 3 and 6 months. On the other hand, there were no significant difference in Vancouver Scar Scales and alar base width between the BTX-A and control groups in 3 and 6 months.Conclusions: Botulinum toxin injection into the orbicularis oris muscle in unilateral complete cleft lip preoperatively shows significant improvement in the cheiloplasty scar.