The Industrial Symbiosis Readiness Level Matrix (ISRLM) tool presented in this paper, was developed to address the challenges inherent in implementing and managing Industrial Symbiosis (IS) networks. IS networks are complex systems involving diverse actors with varying levels of preparedness, perspectives, and priorities, which can result in miscommunication, inefficiencies, and slow implementation and development. To overcome these challenges, the ISRLM tool provides a structured framework for evaluating and visualizing IS readiness, facilitating discussions among actors, creating mutual understanding, and coordinating decision-making. The development of the ISRLM tool followed an iterative process that combined rigorous literature reviews, co-design through stakeholder interviews and workshops, as well as testing and validation within existing IS networks. Drawing on established concepts of readiness level evaluation and incorporating feedback and suggestions of improvement from practitioners and academics, the tool was refined through multiple cycles of testing and evaluation. This co-design approach ensured the tool's relevance and usability across various IS contexts. The ISRLM tool is developed as an interactive Excel-based tool that generates visual outputs based on actors’ evaluation of perceived readiness. It supports IS networks by guiding the implementation process, identifying readiness gaps, and enabling continuous evaluation and improvement. Applicable during both the initiation and development phases of IS collaborations, the tool can enhance trust, help align priorities, as well as guide and accelerate progress toward shared goals.