Rotation-advancement repair (RAR) has been the most widely used technique for unilateral cleft lip repair. We recently used a straight-line repair with medial orbicularis muscle lengthening (SLR-ml) technique, based on the hypothesis that it could minimize the postoperative scar appearance without causing s short-lip deformity when muscle reorientation is performed correctly. A retrospective cohort study was conducted on unilateral complete cleft lip patients who underwent cheiloplasty between 2009 and 2017. Two cheiloplasty techniques were compared: RAR and SLR-ml. Outcomes were evaluated by assessing follow-up photographs using three methods: (1) glance impression on a five-point scale, (2) Manchester Scar Scale, and (3) indirect anthropometry. Seventy-one patients were analysed: 41 in the RAR group (28 male, 13 female) and 30 in the SLR-ml group (15 male, 15 female). The glance impression (P = 0.506) and Manchester Scar Scale (P = 0.347) scores did not differ between the groups. According to the symmetry ratio (cleft side value/non-cleft side value), vertical lip height (P = 0.804), horizontal lip length (P = 0.881), and Cupid's bow width (P = 0.122) did not differ significantly between the groups. The preoperative lip height discrepancy was not correlated with the postoperative vertical lip height. The SLR-ml method can be regarded as a successful tool for symmetric repair of unilateral cleft lip.