Attention-Deficit/Hyperactivity Disorder is one of the most common mental disorders in childhood, and it continues to adulthood without proper treatment. Stimulants have been used in the treatment of Attention-Deficit/Hyperactivity Disorder (ADHD) for many years, and the efficacy of methylphenidate in the treatment of adults with ADHD has been proven to be acceptable according to meta-analysis studies. However, there are some concerns about stimulants. Finding other effective medications for the treatment of adult ADHD seems necessary. We hypothesized bupropion could be effective in the treatment of adult ADHD because some theoretical and experimental evidence exists to support efficacy of this medication. Forty-two patients with a diagnosis of ADHD, according to the revised fourth edition of the Diagnostic and Statistical Manual of Mental Disorders, were randomized to receive 150 mg/day bupropion or placebo for a 6-week double-blind, placebo-controlled clinical trial. Each patient filled the Conners' Adult ADHD Rating Scales-Self-Report-Screening version (CAARS) before starting to take medication and in weeks 3 and 6 of the study. The mean score of the two groups receiving bupropion or placebo decreased over the 6 weeks. There was a significant difference between the two groups in CAARS score after 6 weeks. Bupropion is more effective than placebo in the treatment of adults with ADHD. Bupropion can be an alternative medication for the treatment of Adults with ADHD as its clinical efficacy was proven by other studies.