Individuals suffering from chronic fatigue syndrome and healthy controls watched a series of 30s video-clips previously selected to induce fatigue (e.g., a person carrying home heavy grocery bags), anxiety, or relaxation. Participants received the instruction to imagine themselves in that situation (e.g., “imagine yourself doing your shopping at the supermarket and then carrying home heavy bags”). Results showed that participants reported higher levels of fatigue after having imagined a fatiguing situation, compared with an anxiety provoking or relaxing situation. Although this effect was found in both groups, individuals with chronic fatigue syndrome reported higher levels of fatigue than controls. This study demonstrates that observing an effortful task while merely forming a mental image of performing that task may be sufficient to provoke fatigue.