A method and system for controlling application of MU-MIMO. The disclosure provides for considering a device's block error rate (BLER) as a basis to decide whether to provide the device with MU-MIMO service. For instance, a base station could determine which of the base station's served devices each have threshold low BLER. And on at least that basis, the base station could select each such device to receive MU-MIMO service. Or faced with a choice between devices to receive MU-MIMO service, the base station could compare the devices' levels of BLER and could select the devices that have lower BLER to receive MU-MIMO service.