Urbanization poses increasing threats to environmental sustainability and public well-being. While urban green and blue spaces deliver critical ecosystem services such as biodiversity maintenance, and mental health benefits, these are often overlooked in policy decisions due to their non-market nature. This study applies a discrete choice experiment to evaluate citizens’ preferences and willingness to pay for improvements in five biodiversity-related ecosystem services—flood control, disease control (biological control of potentially harmful species), clean drinking water, CO₂ sequestration, and pollinator habitat—within public parks in Brescia, Italy. Based on environmental economics and welfare theory, the discrete choice experiment represents a hypothetical market simulation for the evaluation of goods not traded on existing markets. An informational treatment was also incorporated to improve understanding and simulate realistic trade-offs. A mixed logit model, capturing individual-level heterogeneity, was employed to analyze responses from 500 residents. Results revealed statistically significant and positive preferences for all five ecosystem services, with the highest willingness to pay for clean drinking water (€0.815 per year per 1% improvement), followed by pollinator habitat and disease control. The analysis highlights strong public support for biodiversity-enhancing interventions and provides robust empirical estimates for integrating ecosystem services economic values into urban planning. This research contributes to natural capital accounting and equity-focused policy design by illustrating the societal demand for greener, healthier cities.