Objective: To examine the naturalistic response to and cardiovascular side effects of stimulant medication in older adults with ADHD. Methods: Electronic Health Record (EHR) data of adult patients with ADHD (≥55 years) at the specialized PsyQ outpatient clinic for adult ADHD (n = 113, 55-79 years) were collected. Response, cardiovascular status, side effects, and provided medical care before and after the first ADHD medication dose have been recorded. Results: A total of 65% of the patients reported positive response to the medication, and 42% of the patients quit their medication due to side effects or nonresponse. There was a small but significant decrease in weight and increase in heart rate before and after methylphenidate use. Conclusion: Our results indicate that the use of stimulants may be a relatively safe and effective treatment for older adults with ADHD, under the condition that the cardiovascular parameters are monitored before and during pharmacological treatment. Randomized controlled trials (RCTs) are needed to confirm these findings.