Explanations of relationships between migration and environmental change now focus on multiple interactions, risks in destination and immobility. This research applies behavioural migration theory to examine the extent to which immobile populations experiencing environmental degradation exercise agency with respect to location and, in doing so, elucidates what it means to be trapped. This research uses individual survey data from a migrant-sending area in highland Peru where the population experiences negative health and livelihood impacts from climate-related phenomena. Analysis of these data reveals three reasons for non-migration: high levels of satisfaction, resource barriers and low mobility potential. Immobility in dissatisfied people is more likely to be caused by attachment to place than resource constraints. Thus, the results suggest that trapped populations exist along a continuum. This highlights the need for policy responses differentiated by the mobility characteristics and preferences of the individual. Caution, therefore, must be exercised when labelling populations as trapped and promoting relocation.