Background: Pulmonary hypertension (PH) impairs quality of life, exercise performance and survival. Simple measures to monitor the disease are needed. Objectives: We tested whether actigraphy by a wrist-worn device in the patient's home reflects disease severity in PH patients. Methods: Twenty-three outpatients with pulmonary arterial and chronic thromboembolic PH (15 females), functional classes II-IV, underwent clinical examination and actigraphy over 2 weeks while pursuing their usual life at home. Actigraphies were correlated with clinical data and mean pulmonary artery pressure (mPAP). Deaths, lung transplantations and pulmonary endarterectomy were recorded over 4 years. Results: Actigraphies revealed a mean ± SD daytime activity duration of 14:57 ± 1:14 h with 146 ± 125 activity counts/min. Very severely impaired patients (mPAP 50 ± 7 mm Hg) were inactive for longer periods at night (8:25 ± 1:18 h) and less active during the day (54 ± 44 counts/min) when compared to modestly impaired patients (mPAP 33 ± 7 mm Hg; inactive at night for 6:58 ± 0:39 h; daytime activity 229 ± 148 counts/min, p < 0.05 in all instances). Out of 19 patients followed for 4 years, 5 died and 1 received a lung transplantation. Kaplan-Meier analysis revealed a shorter survival without lung transplantation in patients with a duration of daytime activity of <15 h/day than those with >15 h/day duration (log rank, p = 0.026). Conclusion: A long nocturnal rest and reduced daytime activity recorded by actigraphy are associated with severe hemodynamic impairment and reduced survival in patients with PH. Therefore, wrist actigraphy performed during everyday life in the patient's home holds promise as a simple tool for the assessment of disease severity and prognosis in patients with PH.