Adaptation to climate change is a matter of urgent social scientific analysis. Within the agricultural sector of many developing nations, farmers must make long-term decisions to adapt to climate change impacts in order to provide food security and sustainable livelihoods. However, deeper understanding of farmers’ decision-making, as a key stakeholder group, is of vital importance in forming adaptive land use policy ‘from the bottom-up’. This study investigates the psychosocial factors that influence farmers’ adaptation intention in the critical case of Marvdasht County in Iran – a case that exemplifies agricultural stakeholder decision-making in arid and drought-prone regions. We present a conceptual combination-model grounded in Protection Motivation Theory (PMT), employing a correlational survey among 256 farmer-stakeholders. First, we discuss the relative value of the combined model to understanding adaptation intentions. Second, we find that the factors that represent the externalities of farmers' behaviour need to be more thoroughly integrated in to adaptation planning. Third, we find that farmers’ adaptation intention is directly affected by maladaptation, and indirectly by economic disincentives, barriers to belief in anthropogenic climate change and broader risk perceptions.