The Horizon 2020 project EU 1.5°C Lifestyles aims to mainstream lifestyles aligned with the aspirational target of the Paris Agreement. The project analyzes lifestyle perspectives at the household level and links them to studies of relevant political and socio-economic structures at various levels of government. Within this project, Citizen Thinking Labs were organized in five EU countries to explore the acceptance of and motivations and barriers to changes that could lead to lifestyles compatible with the 1.5°C target. Through a unique mixed-methods approach, including an exploratory board game (the Climate Puzzle), this research generated insights into citizen acceptance by exploring motivations and barriers associated with the acceptance of key lifestyle changes toward 1.5°C. The results confirm previous research in that citizens are more accepting of lower-impact lifestyle options requiring financial investment (e.g., changing lighting and using efficient devices) than higher-impact options that require more substantial behavior changes. Citizens were also motivated by perceived co-benefits for example, concerning health. The research developed insight into the conditions underlying the acceptance of the least preferred options that included plant-based eating and smaller housing. The results also indicated that citizens’ acceptance could be shaped by discussing options with other citizens. Thus, we note the important role citizens may play in devising solutions for overcoming barriers to the acceptance of less-preferred lifestyle options in various contexts. While this study focused on individuals, the findings also underscore the limitations of individual and household agency and the importance of modifying the socio-technical context that shapes behavioral patterns and environmental impacts.