Impaired autonomic control represents a cardiovascular risk factor during long-term spaceflight. Little has been reported on blood pressure (BP), heart rate (HR), and heart rate variability (HRV) during and after prolonged spaceflight. We tested the hypothesis that cardiovascular control remains stable during prolonged spaceflight. Electrocardiography, photoplethysmography, and respiratory frequency (RF) were assessed in eight male cosmonauts (age 41-50 years, BMI 22-28 kg/m²) during long-term missions (flight lengths 162-196 days). Recordings were made 60 and 30 days prior to the flight, every four weeks during flight, and on day 3 and 6 post-flight during spontaneous and controlled respiration. Orthostatic testing was performed pre- and post-flight. RF and BP decreased during spaceflight (p<0.05). Mean HR and HRV in the low and high frequency bands did not change during space flight. However, the individual responses were different and correlated with preflight values. Pulse wave transit time (PWTT) decreased during space flight (p<0.05). HRV reached during controlled respiration (6/min) decreased in six and increased in one cosmonaut during flight. The most pronounced changes in HR, BP, and HRV occurred after landing. The decrease in BP and RF combined with stable HR and HRV during flight suggest functional adaptation rather than pathological changes. PWTT shortening in our study is surprising and may reflect cardiac output redistribution in space. The decrease of HRV during controlled respiration (6/min) indicates reduced parasympathetic reserve, which may contribute to post flight disturbances.