Transmission Electron Microscopy (TEM) requires electron-transparent samples with thickness below 100 nm, and conventional preparation methods involving mechanical polishing followed by electropolishing or ion milling are time-consuming and prone to preparation-induced defects. In this study, an electrothinning process was proposed as an alternative intermediate TEM sample preparation technique. Electrothinning was carried out on 1 mm thick equiatomic NiTi alloy using H2SO4 (20%) and methanol (80%) electrolyte at an operating voltage of 10–15 V for 20 min. The sample thickness was reduced from 1 mm to 55 μm through controlled anodic dissolution without mechanical deformation. Uniform thinning behaviour was observed under optimized conditions, while lower voltages resulted in insufficient dissolution and higher voltages caused localized pitting. TEM analysis confirmed the absence of noticeable mechanically induced defects or deformation features in the electrothinned samples. The proposed method is a cost-effective and efficient alternative for TEM sample preparation in research and industry.