Neurodevelopmental and neurological disorders, including autism, ADHD, and cerebral palsy, are frequently comorbid with impaired performance on standardised tests of intelligence. If effective in improving performance on fluid intelligence tasks, computerised cognitive training could offer an accessible intervention. The purpose of this systematic review was to determine the efficacy of computerised cognitive interventions for children with neurodevelopmental and neurological disorders in studies that included performance on tests of fluid intelligence as an outcome. The Cochrane Review Group search strategy was followed to identify randomised or quasi-randomised controlled trials (RCT), or non-randomised pre and post trials of interventions that measure fluid intelligence in children with neurodevelopmental or neurological disorders. Databases searched were the Cochrane Central Register of Controlled Trials, PubMed, CINAHL, PsycINFO, and ERIC, between July 2017 and June 2018. Methodological quality of included articles was assessed using a modified Downs and Black checklist by two independent reviewers. Quantitative analysis on outcome data from each study was analysed using RevMan 5.3.5 to determine intervention effect size. Sixteen studies met the inclusion criteria. 10 of the 16 studies were RCTs, with six of these demonstrating strong methodological quality. Six studies were single-group pre and post studies. The majority of studies involved interventions to train working memory, while other interventions targeted cognitive flexibility and response inhibition, task switching, emotion recognition and relational framing. Meta-analysis of the RCTs demonstrated no significant effect of computerised cognitive training immediately post-training, and a small significant effect at follow-up. Meta-analysis of the single group non-randomised studies showed a significant medium effect both immediately post-cognitive training and at follow-up. Moderate significant effects were found in studies of weaker methodological quality - single-group non-randomised trials. Considering performance on the fluid intelligence measures used by these studies may be influenced by factors such as practice effects, expectancy effects and maturation, caution should be exercised in determining how much weight to place on evidence of efficacy in non-randomised controlled trials of computerised cognitive interventions. At present, there is limited support for the effectiveness of computerised cognitive interventions in increasing performance on tests of fluid intelligence for children with neurodevelopmental disorders.