Wireless communications systems supporting selective routing of carrier aggregation (CA) and multiple-input multiple-output (MIMO) data streams are disclosed. The wireless communications system includes a signal router circuit communicatively coupled to one or more signal sources. The signal router circuit is configured to receive MIMO and CA communications signals for data transmission from the signal source(s) and distribute the communications signals (e.g., data streams) to remote units communicatively coupled to the signal router circuit. The signal router circuit determines whether to route each data stream in a MIMO configuration, a CA configuration, or both to provide an improved wireless communications environment for mobile communications devices connected to the remote units. The improved wireless communications environment may increase throughput, reduce interference and/or noise, and/or improve the transmission quality of wireless communications signals.