ABSTRACT Background Facial mesotherapy is a minimally invasive cosmetic procedure involving the injection of active substances into the dermis and subcutaneous tissue. Although generally considered safe, complications such as granulomatous inflammation can arise due to improper techniques or unregulated products. This case report highlights the immune response to facial mesotherapy and its clinical management. Materials and Methods A 50‐year‐old woman presented with erythematous, hard, and painless facial nodules three weeks after undergoing mesotherapy in a non‐medical setting. A detailed clinical examination, laboratory tests, histopathological analysis, and immunohistochemical evaluation were performed. Tissue expression of CD3, CD20, and CD68 markers was quantified using morphometric analysis. Statistical analysis was conducted to compare the expression of immune markers. Results Histopathological examination revealed granulomatous inflammation dominated by macrophages. Immunohistochemical analysis showed significantly higher macrophage activity (CD68, mean reaction area: 5,982.76 µm 2 ) compared to T lymphocytes (CD3, 1,775.12 µm 2 ) and B lymphocytes (CD20, 187.55 µm 2 ) ( p < 0.001). Initial treatment included antibiotics, corticosteroids, and topical therapies. Subsequent interventions involved intralesional triamcinolone, oral glucocorticoids, and platelet‐rich plasma therapy. Significant clinical improvement was observed within three months, with satisfactory cosmetic outcomes achieved after one year. Conclusion Granulomatous inflammation is a potential complication of facial mesotherapy, particularly when performed in non‐medical settings. Effective management requires timely diagnosis, a combination of systemic and topical treatments, and long‐term follow‐up. This case underscores the need for standardized mesotherapy protocols and medical oversight to minimize risks.