Dyslexia is a cognitive disorder that affects the evolutionary ability to read, write, and speak in people, affecting the correct learning of a large percentage of the population worldwide. In fact, incorrect learning is caused because the educational system does not take into consideration the accessibility parameters that people with dyslexia need to maintain a sustainable educational level equal to others. Moreover, the use of mobile devices, such as smartphones and tablets, has been deployed in education programs, offering many benefits; however, the lack of accessibility of those devices creates new barriers to students with dyslexia that hinder their education. With the aim of reducing these barriers, this paper presents an approach to the development of accessible serious games games for children with dyslexia. As a case study, a serious game based on a previously proposed serious game development method and a new set of accessibility guidelines for people with dyslexia is presented. The main purpose of the serious video game is to improve the treatment of dyslexia, through the collection of data obtained from two puzzles designed to train certain cognitive areas that affect this disability. This article has a double contribution: on the one hand, the guidelines and the method that can help video game developers and therapists to develop accessible serious games for people with dyslexia and, on the other hand, the two specific serious games that can be used by therapists, family members and people with dyslexia themselves.