There is mounting evidence that patients with severe COVID-19 disease may have symptoms that continue beyond the acute phase, extending into the early chronic phase. Often referred to as 'Long COVID'. Simultaneously, case investigations have shown that COVID-19 individuals might have a variety of neurological problems. The accurate and accessible assessment of cognitive function in patients post COVID-19 infection is thus of increasingly high importance for both public and individual health. Little is known about the influence of COVID-19 on the general cognitive levels but more importantly, at sub functions level. Therefore, we first aim to summarize current level of evidence supporting a negative impact of COVID-19 infection on cognitive functions. 27 studies have been included in the systematic review representing a total of 94,103 participants (90,317 COVID-19 patients and 3,786 healthy controls). We then performed a meta-analysis summarizing the results of 5 studies (959 participants, 513 patients) to quantify the impact of COVID-19 on cognitive functions. The overall effect, expressed in Standardized Mean Differences, is -0.56 [95%CI -0.79 ; -0.34]. To prevent disability, we finally discuss the different approaches available in rehabilitation to help these patients and to avoid long-term complication.