Northern Thailand has been experiencing the impact of climate change due to its fragile agro-ecosystem, inhabited by a resource-poor population. The study, conducted in a mountainous landscape of Doi Mae Salong area in Northern Thailand, explores the farmers' perceptions of climate change, its impact on farming, and adaptation measures undertaken by the two ethnic communities in the area for coping with climate change impacts. The data were collected through a structured questionnaire survey of ninety farm households using the recall approach for the past twenty years. The findings suggest that the farmers have perceived the change in climate pattern of the study area, and its negative impact on farming. Farm households have been trying to cope with the impacts by adapting to alternate farming options and practices using traditional techniques. The impact was perceived to be higher in the community living at higher elevation compared to those at lower elevation. Although autonomous adaptation is occurring in the area, the vulnerability of farm households to the impact of climate change still exists in terms of the lack of knowledge and financial resources.