Background: Positive Behavioural Support (PBS) provides an overarching framework for supporting quality-of-life improvements for people who use challenging behaviour. Rapport, or the lack of it, is well understood as a setting factor for some challenging behaviours. Intensive Interaction is an approach that, among other possible outcomes, can develop rapport and feelings of safety, security and connection. Method: Within an NHS Trust, the Intensive Interaction Service works in partnership with the Intensive Support Team. We present case descriptions of people who used challenging behaviour and received Intensive Interaction support. Changes are described using staff and family interview data. The Intensive Interaction techniques that helped develop rapport at each PBS phase are described. Results: Intensive Interaction was used in all PBS phases. It played a role in preventing placement breakdown for one individual. Conclusion: Intensive Interaction should be considered at initial assessment within PBS so that immediate and important improvements can be made to the person's social and communication experience. It is hoped that Intensive Support Services and all PBS practitioners will use it.