Introduction Older adults show increased postural sway and a greater risk of falls when completing activities with high cognitive demands. While dual-task approaches have clarified an association between cognitive processes and postural control, it is unclear how manual ability, which is also required for the successful completion of cognitively demanding tasks (such as putting a key into a lock), affects this relationship. Method Kinematic technology was used to explore the relationship between postural sway and manual control in healthy younger and older adults. Participants (n = 82) remained standing to complete a visual-motor tracking task on a tablet computer. Root mean square tracking error measured manual performance, and a balance board measured deviations in centre of pressure as a marker of postural sway. Results Older adults displayed poorer manual accuracy and increased postural sway across all testing conditions. Conclusions Cognitive capacity can interact with multiple task demands, and in turn affect postural sway in older adults. Improving our understanding of factors that influence postural control will assist falls-prevention efforts and inform clinical practice.