<p>Blue-Green Infrastructure (BGI) is a key urban strategy for climate change adaptation, playing a crucial role in promoting environmental sustainability. Despite its growing importance, BGI remains insufficiently integrated into spatial planning processes. The research presented in this article aims to assess the applicability of reasoning maps as a new decision support tool and to estimate the impact of spatial policy choices in urban areas. Reasoning maps offer a qualitative, expert-based method for structuring complex decision problems, particularly those involving conflicting interests and uncertain outcomes. In spatial policy, location decisions are rarely made by a single entity; groups of stakeholders collectively negotiate them. Therefore, decision support methods that fail to account for group-based deliberation often fall short in practice. In this study, initial variables (nodes) refer to input planning factors, such as land price, BGI accessibility, or infrastructure costs. In contrast, final nodes are aggregated goals that reflect desired urban outcomes—namely, climate change adaptation, residents’ satisfaction, and increased housing value. Through expert panel evaluations, ten influencing nodes were identified and analyzed across two alternative spatial development scenarios using connection strength operators. The results reveal that greater BGI accessibility—particularly under compact development scenarios—enhances urban climate resilience and strengthens cities' capacity to adapt to environmental risks. That enables more informed and equitable planning aligned with sustainability objectives. The proposed method proved effective as a support tool for spatial decision-making. Recommendations are provided for urban policymakers regarding both the location of residential areas and ensuring equal access to BGI as part of sustainable urban development.</p>