Hyperactivity and inattention is commonly observed in school going children. These are the components of a neurodevelopmental disorder known as Attention Deficit Hyperactivity Disorder which can be identified in few such children. An eleven years girl visiting to the OPD was diagnosed with attention deficit hyperactivity disorder. The treatment protocol for her included psychological and pharmacological interventions. Methylphenidate was prescribed to her, which is a central nervous system stimulant, a commonly used drug for the treatment of ADHD. Rare side effects have been reported with the use of this drug. Hyperhidrosis is one such side effect which was observed in our patient. After that, the dose of methylphenidate was reduced. It was observed that after about 6–month duration, she improved from the condition of excessive sweating