Objective: We aimed to determine what older adults perceive to be need-supportive behaviours of peer walk leaders, drawing primarily from Self-Determination Theory (SDT). Design: Experienced peer leaders (n = 13; Mage = 73.23, SD = 6.55) and walkers (n = 17; Mage = 72.88, SD = 5.79) were recruited from existing walking groups. Individuals who expressed an interest in becoming a peer leader (n = 18; Mage = 72.72, SD = 4.99) or walker (n = 20; Mage = 78.90, SD = 10.45) were recruited from retirement villages. Main Outcome Measures: We conducted semi-structured interviews to identify leader behaviours that support autonomy, competence, and relatedness and analysed the data using framework analysis. Results: We identified eight main themes: eliciting walker interest, acknowledging and adapting to walkers’ requirements, ensuring walkers feel comfortable, cared for, and socially integrated, supporting walker confidence, and promoting success experiences. Inexperienced leaders differed from other sub-groups in what they perceived to be supportive behaviours. Conclusion: Future peer leaders could use the identified behaviours to help older adults feel motivated during group walks. New peer leaders can be educated about potential differences between what they describe as supportive and what walkers and experienced leaders perceive as need-supportive behaviours. © 2021 Informa UK Limited, trading as Taylor & Francis Group.