To obtain an effective condition-based maintenance (CBM) of a fleet of cyber-physical systems (CPSs), the associated supervision and decision support system (DSS) must be efficient tools as well. Through these tools, the human supervisor must have reliable and up to date information on each entity of the fleet as well as the information on the environment around the respective entities. Currently, despite a huge increase in industrial CBM implementation, the same effort has not been reflected on the design and specification of supervision and DSSs. The existing supervision and DSSs present several shortcomings which are problematic especially in the cases of large fleets of CPSs; hence CBM policies tend to be less effective in these cases. In this work, the authors propose a new approach with a set of specifications on the supervision and DSSs for effective CBM implementation. The specifications consist of, firstly, fleets of intelligent CPSs embedded with intelligent processing architectures allowing the communications and information exchange among the CPSs. Secondly, an intelligent virtual agent is embedded in the supervision and DSS in such a way that the human supervisor can communicate with all intelligent CPSs in the fleet via this virtual agent. The virtual intelligent agent will trigger and provide any necessary information to facilitate the supervision and decision making for effective CBM. This approach is intended to be firstly, a human-centred in design and secondly, it should reduce significantly the complexity of the supervisor’s tasks as well as improve the efficiency of CBM policies.