Using the Behaviour Change Wheel, this qualitative study first identifies barriers and facilitators to the delivery of webchat mental health helpline support for young people and then suggests strategies for improvement. Eleven online semi-structured interviews with trained helpline volunteers and staff members from a UK-based charity that offers free online support to young people under age 25 were conducted. Transcripts were analysed using deductive analysis with the Theoretical Domains Framework (TDF) followed by coding for inductive themes. Seven core themes were generated based on the TDF domains of environmental context and resources; social influences; knowledge; memory, attention and decision processes; beliefs about consequences; emotion; and professional role and identity. The findings suggest that strategies focused on enhancing volunteers' knowledge, training and their beliefs surrounding webchat helplines, as well as improving the resources and social support provided by the helpline, can facilitate more effective delivery of webchat mental health helpline support for young people.