Primary palmar hyperhidrosis is a condition with excessive sweating of the palms, which significantly worsens the quality of life of patients. A systematic review according to the PRISMA guidelines analyzed 19 studies from 2005–2024 of botulinum toxin (BoNT) injections in adults with this disease. Duration of BoNT efficacy ranged from 3 to 12 months, with BoNT-A averaging 4.9–9.5 months and BoNT-B 3.8–4.6 months. Higher doses and repeated injections prolonged symptom control, with moderate cases having longer relief than severe cases. Treatment significantly reduced the Dermatology Life Quality Index (DLQI) score. Patient satisfaction was 65–100%, although it decreased over time. BoNT is an effective and well-tolerated treatment with significant relief of symptoms.