Interactions between conduction electrons and quantum fluctuations of ferromagnetic order have seldom been observed in magnetoelectronic devices. We show that current-induced quantum magnetization fluctuations can be detected using a spin-torque nano-oscillator by measuring its linewidth at different temperatures. The relative linewidth in a special dynamic region of the device can distinguish quantum magnetization fluctuations from their thermal counterparts, which is important in understanding magnetization dynamics beyond the mean-field level in magnetoelectronic devices.