Age-related differences on theory of mind (ToM) tasks are well established. However, the literature has been criticised for predominantly relying on tasks with poor ecological validity, and consequently it remains unclear whether these age differences extend to tasks with greater realism. In addition, we currently have a limited understanding of the factors that may contribute to age-related declines in ToM. To address these issues, we conducted two studies that assessed age differences in ToM using multimodal social scene stimuli. Study 1 also examined eye movements to assess whether biases in visual attention may be related to age-related difficulties in ToM, and Study 2 included an assessment of social attention (as indexed by biological motion perception) and working memory to assess whether these capacities may explain age difficulties in ToM. In both studies, the results showed that older adults performed worse than their younger counterparts on the ToM tasks, indicating that age-related difficulties in ToM extend to measures that more closely represent everyday social interactions. The eye-tracking data in Study 1 showed that older adults gazed less at the faces of protagonists in the social scenes compared with younger adults; however, these visual biases were not associated with ToM ability. Study 2 showed that older age was associated with a reduced ability to detect biological motion cues, and this mediated age-related variance in ToM ability. These findings are discussed in relation to competing theoretical frameworks of ageing that predict either improvements or declines in ToM with age.