Little is known about physiological and psychological responses to mental stress in stable patients affected by pulmonary arterial hypertension (PAH). The current explorative controlled pilot study was conducted to investigate whether heart rate (HR) and perceived stress would differ during standardized mental stress testing in PAH patients compared to healthy subjects. Correlation analysis between HR, perceived stress, participants’ psychological status and performance on the mental stress task was also performed. The study included 13 female PAH patients (average age: 44.38 ± 10.88 years; average education: 14 ± 3.07 years; mean duration of illness: 9.15 ± 5.37 years) and 13 female controls similar in age (mean age: 47.85 ± 6.36 years) and education (15.92 ± 1.55 years). Participants performed a standardized 9 min mental stress test (computer based, adaptive math task). HR and perceived stress during the task were compared to resting baseline and correlated with psychological state and task performance. Both HR and perceived stress significantly increased during mental stress in a similar way in both groups. A significant correlation was found between HR and perceived stress. Our data show that moderate mental stress has a comparable effect on HR and perceived stress increase in stable PAH patients and control subjects.