Objectives This study examined the association between executive functions and time perspectives in patients with adult attention-deficit/hyperactivity disorder (ADHD). The executive function including self-management to time, self-organization/problem solving, self-restraint or inhibition, self-motivation, and self-regulation of emotion was analyzed. In addition, the time perspective, including past-negative, past-positive, present-hedonistic, present-fatalistic, future-negative, and future-positive, were investigated. The correlations between the executive functions and time perspectives were analyzed in an adult ADHD patient group. Methods Thirty-six participants were divided into 17 in the ADHD group and 19 in the Control group. The participants conduct psychological tests including Barkley Deficits in Executive Functioning Scale (BDEFS), ADHD Self-Report Scale, and the Swedish Zimbardo Time Perspective Inventory to confirm their executive functions, attention, and time perspectives. The participants were recruited at Samsung Medical Center from April 2017 to November 2018. The collected data was analyzed using a t-test and Pearson correlation analysis. Results The adult ADHD patients group showed significantly higher scores in the BDEFS and ADHD Self-Report Scale than the control group. In time perspective scores, the adult ADHD patients group was higher in the past-negative, present-hedonistic, present-fatalistic time perspectives than the control group. In addition, the adult ADHD patients group was lower in future-positive than the control group. In the adult ADHD patients group, the future-positive time perspectives were negatively correlated with the executive functions. Conclusion These results suggest that the negative time perspective is related to the executive function deficits in an adult ADHD group, particularly in the self-management of time, self-organization/problem solving, and self-motivation.