A stapedius reflex threshold determination system is communicatively coupled with a loudspeaker and a cochlear implant implanted within a patient. The system identifies a baseline evoked response level associated with a baseline acoustic stimulation level too low to trigger a stapedius reflex within the patient. The system directs an electro-acoustic stimulation event to be applied to the patient, including electrical stimulation applied by the cochlear implant at a particular electrical stimulation level and acoustic stimulation applied by the loudspeaker at the baseline acoustic stimulation level. The system determines an evoked response level associated with the applied acoustic stimulation and detects that the stapedius reflex is triggered by determining that the evoked response level is at least a predetermined threshold amount lower than the baseline evoked response level. In response to this detection, the system may determine a stapedius reflex threshold of the patient based on the particular electrical stimulation level.