In this study, we investigated how urbanization affects public perception of green spaces on Jeju Island, South Korea, with a focus on identifying sociodemographic drivers of environmental attitudes and behaviors. We examined the complicated interlinkages between urbanization and the public perception of green spaces on Jeju Island. A mixed-methods approach based on land use and land cover analysis was taken to measure, on the one hand, the land cover changes from the 1990s to the present and to illuminate important transformations in vegetation and urban development. On the other hand, we carried out a comprehensive survey of 692 residents, which revealed which demographic factors, such as income or education, affect the way people perceive green spaces. The results showed that the residents with higher income and/or education levels are more likely to express their love for the greenery of the city, whereas the older generation living in mid-mountain areas are seen as those having the most serious concerns about living environment issues. In addition, the study underscores how critical it is to direct social education programs that can nurture environmental knowledge and civic responsibility among the population.