Sustainable-ecological leisure activities shared between grandparents and grandchildren contribute to their personal, social, and familial development, promoting cohesion, emotional ties, and well-being. These activities also foster respect for the environment and align with the Sustainable Development Goals outlined in Agenda 2030. This study aims to analyze the practice of sustainable-ecological leisure among grandparents and grandchildren in northern Spain during the post-pandemic era. The research employed a combined methodology: quantitative, using an ad hoc questionnaire, and qualitative, through group discussion. The quantitative sample included 350 grandparents with grandchildren aged 6–12, while the qualitative stage involved a discussion group of 9 grandparents with primary school-aged grandchildren. Results revealed that both generations have adopted more pro-environment and prosocial attitudes compared to previous periods. However, grandparents feel the need for more quality time with their grandchildren, as the pandemic has led to a perceived emotional distance. Despite this, grandparents find multiple benefits in these shared leisure practices, primarily enjoying them because they want to spend more time together. The findings highlight the significance of environmental leisure activities, which are seen as satisfying, valuable, and healthy. These activities promote co-learning, intergenerational knowledge, and respect for natural environments.