Background: Recording electrocochleography and Impedance (ECochG) using a cochlear implant electrode array provides a new way of tracking cochlear health following implant surgery. We recorded both daily for three months following implantation to provide insights into the interplay between operative trauma, the tissue foreign body response to the electrode and loss of cochlear function. Methods: We conducted a prospective clinical cohort study in adult subjects with preserved ECochG signal recorded during cochlear implantation. Daily recordings of ECochG response, four-point impedance (4PI), audiometry, and subjective symptoms were made using in-house designed “take-home” kits. Recordings were made for three months following surgery. We investigated the primary outcome of hearing preservation. Results: ECochG amplitude and behavioural audiometric thresholds were highly correlated. The mean time course for restoration of normal cochlear mechanics was 25 days (range 13-47 days). Loss of cochlear function occurred in 11 subjects, either within the first week (no CM recorded) or rapidly over ~10 days, 20-30 days after implantation. A drop in CM amplitude was associated with worse hearing preservation (mean relative hearing loss 68.2% vs 28.2%, p = 0.0004) Traumatic surgery was also associated with poorer hearing preservation (mean relative hearing loss 60.6% vs 39.3%, p = 0.029). the maximum 4PI after surgery was higher in the group who had traumatic surgery (804.6 Ohms vs 539.2 Ohms,p = 0.0391), and in the group with the poorest hearing preservation (>25% relative hearing loss = 1003.5 Ohms vs 25-50% loss = 556.3 Ohms vs < 25% loss = 544.1 Ohms ,p = 0.0230). Conclusion: We present the first insights into post-operative cochlear health and its deterioration after implant surgery, using novel monitoring technology. The electrophysiological parameters of ECochG and 4PI correlate with clinical outcomes of interest and can shed light on the time-course of biological events following cochlear implantation.