Many parents/caregivers experience mental health challenges during the early years of their child’s life. These difficulties not only have a negative long-term impact on child health and development but also incur a significant cost to society. While nature-based interventions show promise for improving mental health and wellbeing, their potential to support parents/caregivers with young children remains under-researched. This study evaluated a nature-based parent/caregiver support intervention for parents/caregivers with children under five situated within a city-centre museum garden. The intervention jointly focussed on supporting parent/caregiver wellbeing and promoting mindful engagement with nature. Using qualitative methods, including semi-structured interviews (n=15), an observation and two workshops to develop a logic model, this study explored the experiences and perspectives of parents/caregivers, facilitators and museum staff regarding the intervention’s perceived impacts and mechanisms of change. The intervention was perceived to promote parent/caregiver wellbeing by providing opportunities to relax and connect with nature, interact with other parents/caregivers and spend time with their children. The evaluation also identified specific characteristics that facilitated these outcomes, including its flexible, free-choice format, a primary focus on parent/caregiver wellbeing and the facilitators’ strong interpersonal skills. Furthermore, the intervention fostered relationships between museum staff, facilitators and families, leading to reported improvements in museum staff wellbeing, job satisfaction and sustained family engagement with the museum. This study suggests perceived acceptability of nature-based interventions in museum settings. However further mixed method research is needed to determine intervention effectiveness, for whom and under what conditions.