Research suggests that older adults find it more difficult than younger adults to flexibly allocate attentional resources between two co-occurring multisensory tasks, such as perceiving speech-in-noise whilst maintaining balance. This attentional control may be reflected in oscillatory alpha activity, with increases in activity reflecting inhibition of different brain regions and decreases reflecting neural activation. However, there is limited research examining how alpha activity during dual-task conditions may change as a function of healthy ageing. This study aimed to investigate how younger and older adults reallocate attentional resources when perceiving speech-in-noise whilst maintaining balance, and how these age-related changes are reflected in alpha activity. Nineteen younger adults (18-35 years old) and sixteen older adults (60-80 years old) were asked to identify words in audiovisual sentences extracted from the Grid corpus. Participants completed this speech perception task with or without background noise, whilst standing in an easy balance position (feet side-by-side) or a difficult balance position (feet in tandem). Throughout the task, fronto-central and parieto-occipital alpha activity was recorded using EEG, to measure activation in brain regions associated with balance maintenance and audiovisual speech perception, respectively. Mixed ANOVAs revealed that all participants produced a weaker speech perception performance in noisy listening conditions. However, speech perception in the noisy listening condition was most accurate when participants stood in a challenging balance position, in contrast to our hypotheses. Whilst these behavioural effects were not reflected by fluctuations in parieto-occipital alpha power, decreases in fronto-central alpha power were greater in clear listening conditions compared to noisy listening conditions. Taken together, the results suggest that increasing cognitive load with a secondary multisensory task may not always be detrimental to balance maintenance in physically and cognitively fit older adults.