Forest dieback due to climate change has severe consequences for the sensitive environments of mountain forests which provide important ecosystem services for local communities, lowlands inhabitants, and visitors. However, this phenomenon is sometimes hard to identify for the lay public as it can manifest as a slow-onset phenomenon with rather inconspicuous signals or as large-scale disturbances like in the case of bark beetle outbreaks. The aim of this contribution is to analyze whether lay people perceive climate change-induced forest dieback in the landscape or not and what kind of damage they identify. To address this issue, we carried out a cross-comparison case-study in two mountain areas in France and Germany. To analyze the data, we introduce an innovative variable clustering approach to identify different groups of respondents based on their perception of climate change and forest dieback. Five groups of respondents—illustrating different degrees of worry—were identified in each case study: the non-alarmist, the carefree, the least informed, the worried, and the alarmist. These results show that both phenomena are not perceived as distant but as happening here and now; and that their perceptions are influenced by local contexts and personal experiences. We finally show that public perception of forest dieback has influenced the agenda setting on the enactment of new forest policies.