Background Capsular contracture is the most troublesome complication in breast implant surgery. Although capsule formation can be seen as a normal reaction to a foreign body, it can induce pain, hardness, deformity, and other pathologic problems. Surgical intervention is required in severe cases, but even surgery cannot guarantee a successful outcome without recurrence. This experimental study confirms that single topical administration of leukotriene antagonist zafirlukast (Accolate, Astrazeneca) reduces peri-implant capsule formation and prevents capsular contracture. Methods Twelve smooth-surfaced cohesive gel implants were implanted in New Zealand White rabbits. These miniature implants were designed to be identical to currently used products for breast augmentation. The rabbits were divided into 2 groups. In the experimental group (n=6), the implant and normal saline with zafirlukast were inserted in the submuscular pocket. In the control group (n=6), the implant and normal saline alone were used. Two months later, the implants with peri-implant capsule were excised. We evaluated capsule thickness and collagen pattern and performed immunohistochemical staining of myofibroblasts, transforming growth factor (TGF)-β1, 2. Results The thickness of the capsules in the experimental group was reduced in both dorsal and ventral directions. The collagen pattern showed parallel alignment with low density, and the number of myofibroblasts as well as the amounts of TGF-β1 and TGF-β2 were reduced in the experimental group. Conclusions We suggest that single topical administration of leukotriene antagonist zafirlukast can be helpful in reducing capsule formation and preventing capsular contracture via myofibroblast suppression, modulation of fibroblastic cytokines, and anti-inflammatory effect.