This paper introduces the Industrial Symbiosis Assessment Tool (IS-AT) as a quantitative method to evaluate companies’ potential for Industrial Symbiosis (IS). IS emerged as a promising avenue for reducing waste and maximising industrial surplus value, yet its implementation is hindered by various barriers, such as business engagement, technical and legislative constraints. The IS-AT attempts to address these challenges by offering a structured approach, focusing on three areas: Environmental Sustainability, Business Maturity, and Input–Output Resources, which are further divided into metrics and units, providing a comprehensive assessment framework. Notably, the IS-AT calculates a total score considering the weights of areas and metrics, along with individual unit scores obtained through a Likert scale. Validation of the IS-AT is demonstrated through a case study in Northern Italy. Preliminary findings suggest a correlation between company size and IS-AT scores, with smaller businesses exhibiting lower scores. Additionally, high Input–Output Resources scores appear advantageous for initiating IS initiatives within specific geographical regions. Future research aims to explore connections between industry classifications and IS-AT scores, as well as conduct detailed analyses of individual units to elucidate data trends and inform further investigation.