Atomoxetine is one of the first-line treatments for attention deficit and hyperactivity disorder (ADHD) and is a non-psychotic drug that reduces noradrenalin reuptake by selectively inhibiting presynaptic noradrenaline transporter. This agent, which has a good history of security, rarely produces side effects related to the urinary system. Although this rare side effect has been mentioned previously in the adults using atomoxetine, this effect is not fully known in children and adolescents. Until today, there are only four cases in the literature related to this subject. This case report will mention about the acute urinary retention, which is thought to be induced by the drug used, in a 7-year-old patient receiving atomoxetine treatment due to ADHD. [Anadolu Psikiyatri Derg 2020; 21(2.000): 222-224]