Research has linked socio-economic disadvantage with marked deficits in pre-school children’s key skills, particularly oral language skills, that affect school readiness. Programmes aimed at addressing this problem have largely focused on helping parents to promote these skills at home. However, given the significant increase in the numbers of children arriving in school with these skill deficits, which has been further negatively impacted by the Covid-19 pandemic, the foundation phase of primary school is an additional environment for targeting language deficits. There is some evidence to suggest that TA-led interventions can be effective when adequate training and support is provided, but currently their support is not being utilised effectively due to limited training opportunities. This feasibility study explored the acceptability of providing a brief, online Dialogic Book-Sharing training to TAs, and whether this training would be effective in upskilling TAs and enabling them to improve the language outcomes of children aged 3-7 years in a school context. Eleven TA-child dyads from five primary schools across North Wales participated. Mixed methods including self-report questionnaires, direct observations, and interviews. These assessed TAs’ use of DBS skills, sense of competence, and perceptions of the training and implementing the skills, as well as assessing the effects of the training on standardised and naturalistic measures of child expressive language. Data was collected at baseline, post-training (2-3 weeks after the final training session) and 4-6 weeks after the 1st follow-up. The results showed that the training had significant positive effects on TAs’ use of reflections and child language abilities post-training. There were small to large sized effects of the training on all TA skills and child expressive language. However, the size of these effects was reduced at follow-up. Thematic analysis revealed TA satisfaction and provided useful feedback to improve the feasibility of implementation in schools. Overall, the results of this feasibility study provide positive evidence for this training being an accessible way for schools to strengthen their prevention infrastructures by professionalising a growing, but relatively untrained, group of the school workforce. This has implications for improving the life trajectories of many children, by improving key school readiness skills in preparation for the more formal instruction of subsequent years of education.