Reading and writing are skills fundamental to growing up in our current society. However, many children with developmental dyslexia struggle with mastering these skills. This not only has consequences for their academic development, but negative experiences (i.e., falling behind compared to peers) also impact their motivation, self-beliefs, and well-being. In the Netherlands, these children can receive treatment aimed to increase phonemic processing and awareness, as well as spelling skills. However, much less time is dedicated to stimulating psycho-social factors that might indirectly promote treatment efficacy. Recent studies in educational and clinical contexts have highlighted the beneficial role of fostering a growth mindset in increasing motivation and mental well-being. In a pilot study conducted by our research group, we found a tentative link between mindset and dyslexia treatment success. Children with stronger negative effort beliefs - which are associated with a fixed mindset - improved less during dyslexia treatment. This was also evident at a behavioral level, where the percentage of completed homework was correlated with negative effort beliefs and fixed reading mindset. Furthermore, parents' spelling mindset about their children was a predictor of their child's spelling improvement during treatment, emphasizing the importance of contextual factors. In our current study, we hypothesize that by offering a growth mindset intervention adapted to children with dyslexia, their motivation for and efficacy of the dyslexia treatment will increase. We aim to investigate this by conducting a randomized controlled trial, following 240 children, 8 to 11 years old, throughout their dyslexia treatment. Prior to this dyslexia treatment, children will receive either the growth mindset intervention or an active control intervention. In this symposium presentation, the pilot results, development process of the tailored growth mindset intervention, and preliminary results will be further discussed.