In Australia, low domestic visitor participation rates in Indigenous tourism have negative effects on its sustainable development. This lax demand remains under-examined in published research. This study uses an attribution-based theory, the folk-conceptual theory of behaviour explanation, to investigate how domestic visitors describe their intentional behaviour to participate, or not, in two Indigenous tourism activities (rockart sites and a cultural centre) situated within Victoria's Grampians National Park. Studies in tourism research using attribution theory remain limited; this appears to be the first using folk-conceptual theory. It adopts a qualitative approach using semi-structured interviews and the photoelicitation method with 50 domestic visitors. Results indicate that visitors are more inclined to link "beliefs" than "desires" regarding their intention to participate in nature-based Indigenous tourism activities with connections with history, culture, and learning. However, despite Indigenous tourism being linked to a nature-based environment in the study area, "valuings", "enabling factors", and "causal history of reasons" affect participation levels. While these findings relate to previous research on motivations and barriers, participants' explanatory choices enable deeper insights into visitors' judgements that could then inform strategies to facilitate long-term sustainable Indigenous tourism growth. Understanding demand is central to Indigenous communities attaining benefits from sustainable tourism.