Industrial symbiosis is increasingly acknowledged as a strategic tool for the realization of industrial ecology and implementation of circular economy. Recently, industrial symbiosis literature was enriched with views and discussions on dynamics, focusing on the process and dynamic character of industrial symbiosis development. However, little attention is given specifically to the emergence of industrial symbiosis, in contrast to its development. In addition, no holistic picture exists envisioning the process through which initial ties come about and the critical factors fuelling this process. The aim of this paper is to set focus on and promote a better understanding of industrial symbiosis emergence as the earliest phase of its development. This study explores two aspects of the industrial symbiosis emergence: the process through which initial ties emerge and the critical factors influencing the transition between phases in the process. Based on an in-depth and systematic review of the existing empirically-based literature and by using a rigorous and iterative content analysis, three key (iterative)phases are identified: 1) awareness and interest in industrial symbiosis, 2) reaching out and exploration of (connections, and 3) organizing. Furthermore, five groups of critical factors (contextual conditions, actors, actors' roles, actors' characteristics, and actors’ activities) are identified to influence the emergence process in different degrees at different times in the process.