Botulinum toxin A has been used to treat wrist and finger spasticity mainly through injection of the forearm flexor muscles. This case study describes its first reported use in managing spastic lumbricals of the hand. A 19-year-old male had significant flexion deformity and hypertonicity of the left wrist and hand, particularly the second through fifth metacarpophalangeal joints, after traumatic brain injury. By using the 0-4 Ashworth scale, spasticity of the lumbricals across the second to fourth metacarpophalangeal joints was rated 2, with persistent clonus of the finger flexors as confirmed by electromyography to the middle and ring fingers, even after botulinum toxin A injection of the flexor digitorum sublimis and profundus muscles. By using the electromyography-guided technique, botulinum toxin A was injected into the first lumbrical of the index finger (12 units), second and third lumbricals of the middle and ring fingers, respectively (15 units each), and fourth lumbrical of the little finger (10 units). At follow-up, clinical and electromyographic examination revealed a significant reduction in tone and clonus of the injected lumbricals. Ashworth scores of the lumbricals from the index to little finger improved to 1. Botulinum toxin A injection of the lumbricals can be beneficial in managing spasticity of these muscles. It is well tolerated and effective at doses of 10 to 15 units. Lumbrical injection of botulinum toxin A is a useful adjunct in our percutaneous armamentarium for managing the spastic hand.