Introduction Assessing the curvature and thickness of the tympanic membrane (TM) is of interest for both ENT specialists and developers of hearing solutions. While the diagnostic potential arises from the relation between eardrum curvature and middle ear pressure as well as thickness changes related to inflammatory processes, knowledge about the individual curvature is essential for fitting innovative hearing aids based on direct mechanical stimulation. Optical coherence tomography (OCT), an interferometric imaging technology based on near-infrared light, enables the morphologic assessment of the TM due to its non-invasive, depth-resolved and fast imaging capabilities. Methods To safely and reliably examine the entire TM, we have developed an endoscopic OCT (eOCT) system with an outer endoscope diameter of 3.5 mm and a wide field of view of 10 mm at a working distance of 10 mm . The use of galvanometric scanners and swept-source OCT engines with 100 kHz or 200 kHz A-scan rate facilitated the acquisition of 3D data within few seconds. Different approaches for distortion correction and TM segementation from the fan-shaped eOCT volumes were tested and validated by phantom, ex vivo and in vivo measurements. Results Although motion artifacts from both the examining ENT specialist and the volunteer reduced the theoretical spatial accuracy of about 15 mum in axial and 45 mum in transverse direction during in vivo measurements, point clouds of the TM surface could be extracted. By using a 3D edge detection algorithm and subsequent fitting, segmented phantom surfaces and TM curvatures from temporal bone specimens and volunteers were used for validation of the projected hearing aid application with in-contact sound transmission. Conclusion Endoscopic OCT is a robust tool for TM curvature and thickness measurements with both clinical and commercial applications. While the demonstrated approach provided sufficient accuracy, motion arifacts could be suppressed by speed and handling improvements.