In a randomized controlled trial, we investigated the effects of karate versus a mindfulness-based stress reduction (MBSR) intervention on well-being and cognitive functioning in older adults. Fifty-five adults (52–81 years old) participated in twice-weekly karate versus MBSR sessions or no training for 8 weeks. In pre- and postassessments, subjective well-being, health, cognitive functioning, and chronic stress were measured. Preassessment hair cortisol served as physiological stress marker. The results showed an improvement for the karate group, but not the MBSR and control group, in subjective mental health and anxiety as well as cognitive processing speed. The MBSR group showed by trend as a decrease in stress. No significant correlation between preassessment hair cortisol and postassessment outcomes could be established. But the higher the level of baseline self-reported perceived stress, the higher the increase in depression, anxiety, and chronic stress. Generally, it can be assumed that karate and MBSR showed only small training effects concerning the assessed emotional and cognitive parameters.