Compensatory hyperhidrosis is an adverse effect of thoracic sympathectomy that can be debilitating, which is why an efficient treatment is demanded. Botulinum toxin is an emerging treatment, not well known yet. We report two cases of compensatory hyperhidrosis following thoracic sympathectomy which were both treated with low doses of botulinum toxin A. The patients, a male and a female, noted a high level of satisfaction with the abolishment of sweating that was maintained up to 10 months. We consider that low doses of botulinum toxin A is a well tolerated, safe and effective treatment for compensatory hyperhidrosis and should be offered as an alternative treatment.