Tai Chi is an ancient exercise originated from China. The slow movements of Tai Chi are not thought to evoke an increase in heart rate above 60% HRM, and yet Tai Chi has been found to improve vascular health. We are interested in the response to a single session of Tai Chi, as a mild physical stressor. The acute response to exercise is very important as a stimulus for adaptation, but to our knowledge, no previous studies have assessed the acute response to Tai Chi. The aim of this study was to investigate the response to a single session of Tai Chi. Blood markers of oxidative stress (lipid peroxidation, antioxidant capacity) and inflammation (IL-6) were assessed along with flow-mediated dilation (FMD) in young (18-25years old) and elderly participants (65–75 years old). Participants visited the laboratory twice to undertake Tai Chi or a control visit. Blood withdrawal and FMD assessment were performed every hour, for 4 consecutive hours. Inflammation at baseline was increased in older participants, compared to young and MDA and IL-6 increased immediately after Tai Chi in both groups. Antioxidant capacity increased immediately and post one hour after Tai Chi in both groups. A single bout of Tai Chi was seen to promote cytokine release and increased antioxidant capacity, and may have a beneficial effect in improving human vasculature via these mechanisms in both old and young.