The objectives of this study were to examine whether elderly tai chi practitioners have developed better knee joint proprioception and standing balance control than control subjects. Tai chi and control subjects (n = 21 each) were matched with respect to age, sex and physical activity level. Passive knee joint repositioning was used to test joint proprioceptive acuity. Control of body sway during static standing and subjects’ intentional weight shifting to eight different spatial limits of stability within their base of support were conducted using force platform measurements. Tai chi users were found to have better knee joint proprioceptive acuity, in that they made less absolute angle error than control subjects in passive knee joint repositioning. No significant difference was found in the anteroposterior and mediolateral body sway during static standing. However, tai chi users initiated voluntary weight shifting in the limits of stability test more quickly than control subjects. Moreover, they could lean further without losing stability and showed better control of their leaning trajectory.