Stress can affect health. There is a growing need for the evaluation and application of professional stress management options, i.e, stress reduction. Mind/body medicine serves this goal, e.g, by integrating self-care techniques into medicine and health care. Tai Chi (TC) can be classified as such a mind/body technique, potentially reducing stress and affecting physical as well as mental health parameters, which, however, has to be examined further. We conducted a prospective, longitudinal pilot study over 18 weeks for the evaluation of subjective and objective clinical effects of a Yang style TC intervention in young adults (beginners) by measuring physiological (blood pressure, heart rate, saliva cortisol) and psychological (SF-36, perceived stress, significant events) parameters, i.e, direct or indirect indicators of stress and stress reduction, in a non-randomised/-controlled, yet non-selected cohort (n=21) by pre-to-post comparison and in follow-up. SF-36 values were also compared with the age-adjusted norm population, serving as an external control. Additionally, we measured diurnal cortisol profiles in a cross-sectional sub-study (n=2+2, pre-to-post), providing an internal random control sub-sample. Only nine participants completed all measurements. Even so, we found significant (p<0.05) reductions of saliva cortisol (post and follow-up), which seems to be an indicator of general stress reduction. A significant decrease in perceived mental stress (post) proved even highly significant (p<0.01) in the follow-up, whereas physical stress perception declined to a much lesser degree. Significant improvements were also detected for the SF-36 dimensions general health perception, social functioning, vitality, and mental health/psychological well-being. Thus, the summarized mental health measures all clearly improved, pointing towards a predominantly psychological impact of TC. Subjective health increased, stress decreased (objectively and subjectively) during TC practice. Future studies should confirm this observation by rigorous methodology and by further combining physical and psychological measurements with basic research, thereby also gaining knowledge of autoregulation and molecular physiology that possibly underlies mind/body medicine.