Background: Problems with cognition, particularly memory, are common in people with multiple sclerosis (MS) and can affect their ability to complete daily activities and can negatively affect quality of life. Over the last few years, there has been considerable growth in the number of randomised controlled trials (RCTs) of memory rehabilitation in MS. To guide clinicians and researchers, this review provides an overview of the effectiveness of memory rehabilitation for people with MS. Objectives: To determine whether people with MS who received memory rehabilitation compared to those who received no treatment, or an active control showed better immediate, intermediate, or longer-term outcomes in their:. 1. memory functions,. 2. other cognitive abilities, and. 3. functional abilities, in terms of activities of daily living, mood, and quality of life. Search methods: We searched CENTRAL which includes Clinicaltrials.gov, World Health Organization (The Whoqol) International Clinical Trials Registry Portal, Embase and PubMed (MEDLINE), and the following electronic databases (6 September 2020): CINAHL, LILACS, the NIHR Clinical Research Network Portfolio database, The Allied and Complementary Medicine Database, PsycINFO, and CAB Abstracts. Selection criteria: We selected RCTs or quasi-RCTs of memory rehabilitation or cognitive rehabilitation for people with MS in which a memory rehabilitation treatment group was compared with a control group. Selection was conducted independently first and then confirmed through group discussion. We excluded studies that included participants whose memory deficits were the result of conditions other than MS, unless we could identify a subgroup of participants with MS with separate results. Data collection and analysis: Eight review authors were involved in this update in terms of study selection, quality assessment, data extraction and manuscript review. We contacted investigators of primary studies for further information where required. We conducted data analysis and synthesis in accordance with Cochrane methods. We performed a 'best evidence' synthesis based on the methodological quality of the primary studies included. Outcomes were considered separately for ‘immediate’ (within the first month after completion of intervention), ‘intermediate’ (one to six months), and ‘longer-term’ (more than six months) time points. Main results: We added 29 studies during this update, bringing the total to 44 studies, involving 2714 participants. The interventions involved various memory retraining techniques, such as computerised programmes and training on using internal and external memory aids. Control groups varied in format from assessment-only groups, discussion and games, non-specific cognitive retraining, and attention or visuospatial training. The risk of bias amongst the included studies was generally low, but we found eight studies to have high risk of bias related to certain aspects of their methodology. In this abstract, we are only reporting outcomes at the intermediate timepoint (i.e., between one and six months). We found a slight difference between groups for subjective memory (SMD 0.23, 95% CI 0.11 to 0.35; 11 studies; 1045 participants; high-quality evidence) and quality of life (SMD 0.30, 95% CI 0.02 to 0.58; 6 studies; 683 participants; high-quality evidence) favoring the memory rehabilitation group. There was a small difference between groups for verbal memory (SMD 0.25, 95% CI 0.11 to 0.40; 6 studies; 753 participants; low-quality evidence) and information processing (SMD 0.27, 95% CI 0.00 to 0.54; 8 studies; 933 participants; low-quality evidence), favoring the memory rehabilitation group. We found little to no difference between groups for visual memory (SMD 0.20, 95% CI -0.11 to 0.50; 6 studies; 751 participants; moderate-quality evidence), working memory (SMD 0.16, 95% CI -0.09 to 0.40; 8 studies; 821 participants; moderate-quality evidence), or activities of daily living (SMD 0.06, 95% CI -0.36 to 0.24; 4 studies; 400 participants; high-quality evidence). Authors' conclusions: There is evidence to support the effectiveness of memory rehabilitation on some outcomes assessed in this review at intermediate follow-up. The evidence suggests that memory rehabilitation results in between-group differences favoring the memory rehabilitation group at the intermediate time point for subjective memory, verbal memory, information processing, and quality of life outcomes, suggesting that memory rehabilitation is beneficial and meaningful to people with MS. There are differential effects of memory rehabilitation based on the quality of the trials, with studies of high risk of bias inflating (positive) outcomes. Further robust, large-scale, multi-centre RCTs, with better quality reporting, using ecologically valid outcome assessments (including health economic outcomes) assessed at longer-term time points are still needed to be certain about the effectiveness of memory rehabilitation in people with MS.