<p>The rapid rise of sharing economy-related business models, such as short-term rental platforms, raises the questions of how these business models influence the natural environment and what environmental actions are available to both hosts and tenants to reduce environmental impact. Different from many studies addressing the role of guests’ behaviours to decrease their environmental impacts related to short-term rental, the role of hosts is still under-researched. The objective of the study is to examine the factors influencing hosts’ pro-environmental behaviour (such as increasing resource and energy efficiency, improving waste management practices)—a novel area that has been previously underexplored and important from the perspective of the overall environmental impact of the short-term rental sector. By extending the Theory of Planned Behaviour with the concept of prosumption, the research surveyed 112 short-term rental hosts in Hungary using a PLS-SEM approach. Findings support the research hypotheses, showing that general attitudes toward prosumption, environmental attitudes, subjective norms, and perceived behavioural control significantly impact hosts’ pro-environmental behaviour. Notably, attitudes toward prosumption showed the strongest influence. Results imply that beyond creating positive environmental attitudes to short-term rental hosts, it is also important to promote positive attitudes to prosumption activities in general in order to foster pro-environmental behaviour among hosts. These insights are crucial for enhancing the sustainability performance of the short-term rental sector and other branches of tourism where prosumer behaviour is prevalent, thereby delivering societal benefits.</p>