As cities grapple with the escalating challenges of urban heat and its impacts on vulnerable populations, particularly older adults, green spaces are increasingly promoted as effective urban cooling solutions. However, despite the extensive literature on people's access to and preferences for urban green spaces, little is known about the perception and use of these spaces as nature-based climate shelters on hot days, especially by older adults. This study focuses on Barcelona, a Mediterranean city facing rising temperatures, to explore older adults' patterns of use and preferences for urban green spaces on hot days. The research aims to: 1) analyze heat coping behaviors, emphasizing visits to urban green spaces; 2) identify crucial characteristics of green spaces for older adults; and 3) assess variations in behaviors and preferences based on socio-demographic factors. The study leverages survey data from 291 older adult residents, combining face-to-face and online formats. Results indicate that 54 % of older adults use urban green spaces for cooling on hot days, with preferences for morning or evening visits. Factors influencing non-visitation include perceived lack of thermal comfort, noisiness or crowdedness, and proximity issues. Alternative heat coping strategies include staying at home, traveling to cooler areas outside the city, visiting blue spaces, or air-conditioned indoor facilities. Preferred green space characteristics include abundant shade, leafy vegetation, accessibility factors (e.g., walkability), urban furniture (e.g., benches), and water features. Socio-demographic differences reveal higher green space use among younger age groups and residents in certain districts. Mobility limitations and lower education levels influence preferences, with mobility-challenged individuals prioritizing accessibility aspects. Lower-educated respondents are more likely to report barriers to accessing green spaces. These findings highlight the need for tailored urban planning strategies, considering sociodemographic variations, to mitigate heat-related health risks for older adults. By prioritizing green space accessibility, enhancing its quality, promoting its cooling benefits, addressing cooling inequalities and integrating climate considerations in urban green planning, cities facing increasingly pressing heat challenges can create climate-resilient and inclusive green environments that prioritize the well-being of their aging populations.