From its conception, 5G has been designed to support a wide variety of service types, ranging from enhanced mobile broadband (eMBB) to ultra-reliable low-latency communications (URLLC). To overcome the disparity of their requirements, a number of radio resource management (RRM) solutions have been proposed, among which multi-connectivity (MC) may be highlighted. That is, the aggregation of radio resources in the shape of component carriers (CC) from several base stations (BS). MC allows a number of benefits to be achieved: from increased reliability due to multi-link diversity, to throughput enhancements, due to the usage of additional radio resources and load balance among the involved BSs. This paper proposes a novel RRM mechanism to jointly manage user equipment (UE)-BS association rules and CC selection, according to network operators’ policies, defined over a variety of performance indicators. Simulations show that, in a scenario of load imbalance, the proposed mechanism allows the UE throughput to be increased while improving the network efficiency by means of a proper inter-CC and inter-BS load balance when compared to traditional received power-based schemes for CC management, applied in a MC environment.