Concentration and memory impairment (named “brain fog”) represents a frequent and disabling neuropsychological sequela in post-acute COVID-19 syndrome (PACS) patients. The aim of this study was to assess whether neurocognitive function could improve after a multidisciplinary rehabilitation program enhanced with individualized neuropsychological treatment. A prospective monocentric registry of PACS patients consecutively admitted to our Rehabilitation Unit was created. The Montreal Cognitive Assessment (MoCA) was used to assess cognitive impairment at admission and discharge. A total of sixty-four (64) PACS patients, fifty-six (56) of them with brain fog, were treated with a day-by-day individualized psychological intervention of cognitive stimulation (45 min) on top of a standard in-hospital rehabilitation program. The mean duration of the acute-phase hospitalization was 55.8 ± 25.8 days and the mean in-hospital rehabilitation duration was 30 ± 10 days. The mean age of the patients was 67.3 ± 10.4 years, 66% of them were male, none had a previous diagnosis of dementia, and 66% of the entire sample had experienced severe COVID-19. At admission, only 12% of the patients had normal cognitive function, while 57% showed mild, 28% moderate, and 3% severe cognitive impairment. After psychological treatment, a significant improvement in the MoCA score was found (20.4 ± 5 vs. 24.7 ± 3.7;p< 0.0001) as a result of significant amelioration in the following domains: attention task (p= 0.014), abstract reasoning (p= 0.003), language repetition (p= 0.002), memory recall (p< 0.0001), orientation (p< 0.0001), and visuospatial abilities (p< 0.0001). Moreover, the improvement remained significant after multivariate analysis adjusted for several confounding factors. Finally, at discharge, 43% of the patients with cognitive impairment normalized their cognitive function, while 4.7% were discharged with residual moderate cognitive impairment. In conclusion, our study provides evidence of the effects of multidisciplinary rehabilitation enhanced with neuropsychological treatment on improvement in the cognitive function of post-acute COVID-19 patients.