Portable consumer health management devices are increasingly gaining attention from health consumers. StressEraser is a portable biofeedback device widely advertised as a stress reliever and cognition enhancer. However number of evaluation studies assessing effect of StressEraser on cognitive performance improvement and stress relief is very limited. The purpose of this study was to evaluate the effect of StressEraser on cognitive performance and stress relief using a crossover design. A computerized psychomotor vigilance task (PVT) was selected as a mental stressor. The cognitive performance and stress level were measured in fourteen subjects having two 10-minute PVTs and 10-minute StressEraser intervention in between the PVTs. All main PVT metrics of cognitive performance (MeanRT, MedianRT, and Fastest 10%) became significantly worse after StressEraser application (P<0.05). On the other hand, six heart rate variability (HRV) parameters (MeanRR, SDNN, RMSSD, aLF, aHF, and LF/HF) used to assess stress level showed no significant differences between the first and the second PVTs. Furthermore, the subjective stress levels reported by the study subjects after the first and the second PVTs were not significantly different. We concluded that the StressEraser had a negative effect on cognitive performance and no effect on stress level.