Background: The purpose of this systematic review is to synthesize the existing literature reporting the effects of computerized cognitive trainings on the executive functions of children with ADHD. Method: A systematic review was carried out following the PRISMA statement; the primary sources used were five electronic databases (Scopus, Science Direct, Pubmed, Springer, Taylor & Francis). Results: 20 articles met the eligibility criteria, data on the training characteristics and the effects on executive functions were extracted, followed by an analysis of bias and the methodological quality of the studies. The results of the studies were widely heterogeneous, largely associated with the variety of training programs and the measurement instruments used. The most studied executive functions were working memory and inhibitory control. Some of the studies reported that the intervention led to significant effects on working memory and attention ( N = 7), and improvements in inhibitory control ( N = 5) and planning ( N = 4) were also reported. At the same time, others did not report the effects of the intervention on these processes. The assessment of the quality of the evidence showed important risk biases among the reviewed studies. Conclusion: Some training based on computer systems showed positive effects on the executive functions of working memory, attention, and inhibitory control in children with ADHD. However, other training sessions did not show significant effects. In general, the evidence shows mixed results, a high diversity of measurement instruments, and high risks of bias between the studies. Therefore, the evidence has not been consistent about the general benefits of computerized training on the executive functions of children with ADHD.