With an aging population, detecting cognitive dysfunction at an early stage is important. However, no current neurophysiological assessments examine brain activity status in community-dwelling older adults. Therefore, this study aimed to determine the relationship between event-related potential (ERP) and neuropsychological scores during go/no-go tasks among community-dwelling older adults. The participants were 34 young adults and 46 older adults. They underwent a go/no-go task to measure ERP, and older adults also underwent neuropsychological testing. Older adults were divided into two groups for analysis based on the results of the Japanese version of the Montreal Cognitive Assessment (MoCA-J): cognitively normal and cognitively impaired. N2 latency was significantly delayed in the cognitively impaired group compared to the cognitively normal and younger groups. In addition, the younger group exhibited a significant increase in P3 amplitude and faster latency compared to both older adults groups, with no notable difference between the two older adult groups. Results of a correlation analysis between ERP and neuropsychological test scores showed that the N2 latency was correlated with neuropsychological test scores, which suggested that receiver operating characteristic (ROC) curve analysis could discriminate cognitive function. These results indicated that the N2 latency reflected potential cognitive dysfunction in community-dwelling older adults. Furthermore, P3 amplitude may be useful in detecting age-related decline in inhibitory function.