This paper deals with the interactions between the twoscientific communities of AI and Complex SystemsSciences. Theterm “complexity” is used since the 80’s to refer to alargely interdisciplinary endeavour, aimed atunderstanding common organizational and dynamicalproperties of nonlinear systems.The interactions between the two communities ofCSS and AI have been so far rather limited, althoughboth might benefit from closer encounters. Recentdevelopments in the context of agent-based modellingand simulation, which is receiving a growing interest invarious fields from biology to social simulation, representa new opportunity for further exploring andstrengthening these interactions and connections, inparticular between CSS and Multi-Agent Systems(MAS) .