peer reviewed ; Background : Improving the features of teachers’ linguistic interactions with students is currently an emphasis on many efforts to increase the benefits of early education programs on children’s language development. SOLEM “Soutenir et Observer le Développement du Langage de l’Enfant en Maternelle » is a support tool designed for teachers to observe and sustain children’s language development in classroom environment. SOLEM positive outcomes have been already demonstrated. However, its implementation in preschools requires a close collaborative work between teachers and Speech and Language Therapists (SLTs) to greatly increase its effects. Aims: This study is aiming at describing a professional development program targeting SLTs enabling them to train teachers to implement SOLEM in Belgian preschools. We focused on how teachers are taught by SLTs to implement support practices following SOLEM strategies. Method: A mixed method design, including sharing information, modeling, prompting and providing feedback, was used to assess direct individualized in-site interventions. Eleven pair-working teachers and SLTS participated in the study. Specific individualized targets of SOLEM strategies were presented, discussed and assessed across the intervention for each pair of professionals. Teacher’s knowledge and self-reported practices were assessed through a questionnaire before and following the implementation. Interviews were conducted with both groups of professionals during and following the implementation. Qualitative data was then thematically coded. Results: Analysis found that the program strengthened collaborative partnerships between SLTs and teachers as well as teachers’ knowledge and use of language rich strategies. SLTs professional identities were enhanced through the professional learning as well as their self-efficacy. Modeling and feedback were identified as key factors to sustained practices change. Conclusion: Outcomes illustrate how individualized professional learning can improve ...