Background: Extensive Hailey–Hailey disease is often resistant to conventional topical and systemic therapies. The systemic and ablative therapies have many side effects and/or high recurrence rates. Therefore, an alternative safe and effective treatment is needed. Objective: To assess the effectiveness of botulinum toxin type A in the treatment of extensive Hailey–Hailey disease. Methods: The cases of six patients with extensive Hailey–Hailey disease resistant to multiple therapeutic regimens were studied and described. Adjuvant therapy with botulinum toxin type A/Dysport^® was started in all six cases. Results: Marked improvement of the lesions was achieved with few side effects in all patients. Conclusion: Botulinum toxin type A is a safe and effective adjuvant treatment for extensive Hailey–Hailey disease.