There is some evidence that cognition may be impaired during multiple sclerosis (MS) relapse. The aims of this study were to assess the cognitive status with the Brief International Cognitive Assessment for Multiple Sclerosis (BICAMS) in MS patients during relapse, in stable patients, and in healthy controls; to evaluate cognitive changes up to 3 months after relapse; and to estimate the impact of different factors on cognition after relapse. BICAMS was performed in 60 relapsing, 30 stable patients and 30 controls. Relapsing MS patients were assessed during relapse and one and three months after relapse. SDMT score was lower in relapsing than in stable patients. The mean scores of all BICAMS tests were higher one month after relapse than during relapse (p < 0.001). SDMT score after relapse improved in younger patients, who had more severe relapse (p < 0.05). BVMT-R score improved more in men, in patients with biologically active interferon-beta, in patients treated with methylprednisolone and in patients who were rehabilitated (p < 0.05). CVLT-II score improved in women and in patients with shorter relapse (p < 0.05). A neuropsychological assessment, like the evaluation of physical disability, is important during relapse. BICAMS may be suitable for a quick and effective assessment of cognition during relapse.