Background: In this paper, we report the results of an action research conducted to design a communication device to help a non-verbal child develop language skills. Participatory design (PD) is frequently regarded as a convenient approach for designing high assistive technology (HAT) for people with serious speech impairments. However, our literature survey has shown that PD is used in an ad hoc fashion, and so a methodological framework for the inception, construction, and evaluation of HATs is still missing. Methods: PD4CAT, a participatory design method for customized assistive technology, was used to direct this research.Results: This method led to the engagement of an impaired child (besides other participants) as a co-designer of a customized assistive technology for his own use. The system resulting from actions performed during this research has helped the child in his rehabilitation process by means of the customized assistive computational technology developed within PD4CAT. Conclusion: The contributions of this action research include the improvement of PD4CAT by means of guidelines to engage a non-verbal child in participatory design practices, in order to incept his assistive computational technology.