The quality of the interaction between mothers and their children with an Intellectual Disability (ID) plays a crucial role in their development and in particular during adolescence. This qualitative study was designed to provide a better understanding of aspects of the relationships between mothers and their adolescents with ID through an art-based tool, the Joint Painting Procedure. The qualitative analysis of six dyads of mothers and adolescents with severe, moderate and mild ID was based on the principles of narrative and phenomenological inquiry. The findings yielded three key themes that emerged from the relational dynamics during the JPP: (1) from dependency to autonomy, (2) the joint painting as a way to foster verbal communication, and (3) playfulness and enjoyment. The JPP appeared to serve as a meaningful art-based assessment of the implicit and explicit aspects of the relationships which evolved during the interaction. The findings underscore the potential of the JPP as a non-verbal, art-based tool that allows researchers and clinicians to learn more about the dynamics of relationships between mothers and their adolescents with ID. It also enables a context where the expression of relational issues can be communicated and even transformed.