Demand for less-invasive procedures for treating gummy smile, such as botulinum toxin A injections, has increased substantially over the years. Meanwhile, the optimal injection site for botulinum toxin A injection is debated. The authors aimed to investigate the efficacy of botulinum toxin A injection at the Yonsei point for treating gummy smile. In this double-blind, single-site, randomized clinical trial, healthy participants with a gummy smile (anterior gingival exposure of ≥3.0 mm) were enrolled and randomized (1:1 ratio) into two groups. The experimental group was administered 6 U of botulinum toxin A at the Yonsei point (a single-site injection of 3 U to the right Yonsei point and 3 U to the left Yonsei point), and the control group received the same dose in the bilateral levator labii superioris alaeque nasi muscle sites. The patients were assessed at baseline and 4, 12, 24, and 48 weeks after the first injection using a digital vernier caliper. A total of 49 participants were enrolled. Anterior and bilateral posterior gingival exposure were reduced at 4, 12, and 24 weeks ( P ≤ 0.05) and returned to baseline at 48 weeks in both groups; there was no difference between the groups at these time points. The increase in satisfaction among patients was significant, and few adverse events were observed. Both the Yonsei point and the levator labii superioris alaeque nasi muscle site can be used as botulinum toxin A injection sites for treating gummy smile. Therapeutic, I.