Dividing attention between cognitive and motor tasks, such as walking while responding to auditory cues in a conversation, is a frequent challenge in everyday life. When demands exceed available cognitive resources, performance can suffer, increasing the risk of falls. While previous research has shown mixed results regarding cognitive-motor interference (CMI), growing evidence suggests that the type of walking, treadmill versus overground, may influence dual-task performance. We therefore examined how the gait context affects cognitive performance.Thirty-one participants completed an auditory Go/No-Go task under three conditions: while seated (single-task baseline), walking on a treadmill (indoor dual-task), and walking outdoors (outdoor dual-task). Sensitivity (d’) and response times were analyzed to assess interference effects. We hypothesized reduced d’ and slower responses during both types of dual-tasking compared to single-tasking, with greater CMI during outdoor dual-tasking, due to increased motor demands.We found significantly lower d’ and longer response times in both walking conditions compared to the sitting condition. Notably, the increase in response time was most pronounced during outdoor walking, while the decline in d’ scores was more marked during indoor walking. Heart rate was elevated during both dual-task conditions similarly, reflecting comparable physiological load.The findings highlight that CMI results are shaped by task demands and environmental context. They also emphasize the importance of more naturalistic experimental designs. In future work, the analysis of concurrently recorded functional brain activity could help identify the neural mechanisms underlying CMI in everyday contexts, offering insights relevant to fall prevention, aging, and mobile brain-body research.