Introduction: Tinea unguium, or onychomycosis, is a common fungal infection affecting the nails, particularly prevalent among the elderly, and is primarily caused by dermatophytes like Trichophyton mentagrophytes. This report highlights a case of onychomycosis in a male patient with plantar hyperhidrosis, treated with a combination of itraconazole and Mentholatum ointment, aiming to improve understanding of the disease, its predisposing factors, and effective treatment approaches. Case: A 38-year-old Batak man presented with discolored, thickened toenails, mainly affecting the fourth toe of his left foot, which had persisted for five years. Physical examination and OSI assessment identified severe tinea unguium in the fourth toe, with mild involvement in the fifth toe. Diagnostic tests including KOH analysis and dermoscopy supported the diagnosis of onychomycosis. The treatment plan involves pulse-dose itraconazole and topical application of a camphor, menthol, and essential oil ointment, with comprehensive patient education on adherence and preventive measures. Follow-up is scheduled in four weeks to monitor progress and adjust treatment as needed. Conclusion: A male patient with plantar hyperhidrosis and tinea unguium caused by Trichophyton mentagrophytes was diagnosed through history, physical examination, and tests. He is undergoing combination therapy with pulse-dose itraconazole and a camphor, menthol, and essential oil regimen, showing significant clinical improvement after 4 weeks, with further follow-up planned and a prognosis considered dubius ad bonam.