An exploration into the understanding of the underpinning Self-Determination Theory framework in NS’s intervention. Abstract Based on Self-Determination Theory, this study aimed to explore mentors’ behaviours when delivering sessions to their often-disengaged participants, in an informal education and wellbeing intervention. Much of the current research focusing on needs-supportive behaviours has been conducted in formal education settings such as schools and colleges, so exploring needsupportive behaviours used in informal settings can provide useful knowledge to the field. Three research questions were addressed in this study throughout a two-phase approach: how do mentors use certain strategies to help promote a needs-supportive environment for participants in the reflection interactions? How do mentors position themselves and their participants to create opportunities to satisfy their participants’ autonomy, competence and relatedness needs? What experiences do mentors have using certain behaviours in order to facilitate a needs-supportive environment with their participants throughout the 10-week intervention? In phase 1, content analysis was used to gather how often autonomy, competence and relatedness supportive statements and questions were used by mentors throughout the reflection data. Additionally, positional theory was used to help understand why mentors may use certain behaviours when they occupy certain roles in social interactions with their participants. In phase 2, semi-structured interviews were conducted with six mentors from the Noise Solution intervention. Interviews were deductively analysed using thematic analysis. Findings revealed mentors positioned themselves as the ‘facilitator’ and ‘friend’, whilst inviting participants to take up the position of the ‘expert’. All positions could lead to certain needs- supportive behaviours being delivered by mentors. The findings from phase 2 suggest that providing choice and placing participants at the centre of the intervention helped to satisfy autonomy, highlighting participant’s self-worth helped to satisfy competence and gaining a professional ‘friendship’ helped to satisfy relatedness needs. The findings are discussed, limitations are identified and suggestions for future research are noted. Key Words: Needs-supportive behaviours, Self-Determination Theory, Intervention, Autonomy, Competence and Relatedness