Purpose Previous research has established that lie‐detection accuracy decreases with age; however, various mechanisms for this effect have yet to be explored, particularly when examining the detection of children’s lies. The present study investigated if younger and older adults detect children’s lies using different cues (verbal content, verbal auditory, non‐verbal, global traits) to explore if cue usage may help to explain this age‐related decline. Method A total of 100 younger (18–30 years) and 100 older adults (66–89 years) watched child interview videos (half were truth‐tellers; half were lie‐tellers coached to conceal a transgression). Participants provided veracity judgements (truth vs. lie) and described the cues that they relied on to make their judgements. Results Older adults used marginally significantly fewer verbal content and significantly more global trait cues compared to younger adults. The use of global trait cues partially mediated the age‐related decline in detection accuracy. Conclusion These results present a partial mechanism for the age‐related decline in deception detection. This can inform psychological theory on how ageing affects perceptions of child witnesses and deception detection abilities.