Standing postural control is known to be altered during aging, but age-related changes in sitting postural control have scarcely been explored. The present experiment studied the roles of visual and haptic information in a sitting task in both young and older adults. Fifteen young and fifteen older adults participated in this study. Six experimental conditions were performed with eyes open and eyes closed: quiet sitting, rocker-board sitting, and 4 conditions of haptic supplementation, provided by a hand-held pen, during rocker-board sitting. Classical variables were extracted from the center of pressure (COP) and pen trajectories, and the stabilogram diffusion analysis was performed on the COP data. Three-way ANOVAs (Group x Vision x Condition) were carried out. Postural instability was strongly attenuated by haptic supplementation in both age groups. Furthermore, instability due to visual deprivation was compensated by haptic supplementation. Long-and short-term diffusion coefficients were smaller in conditions of haptic supplementation. The present study confirmed the effect of haptic supplementation on both open-loop and closed-loop mechanisms of postural control and extended it to unstable sitting in young and older adults despite the complex biomechanical systems involved in sitting postural tasks. (C) 2014 Elsevier Ltd. All rights reserved.