A method and system for controlling application of MU-MIMO. The disclosure provides for considering a device's power headroom 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 power headroom. 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 power headroom and could select the devices that have lower power headroom to receive MU-MIMO service.