This review focuses on the SAXS and WAXS analysis of the collagen structure of leather, from pioneering works through to recent developments. X-ray scattering can be used to investigate the structural features of fibrillar collagen in the leather matrix, including axial periodicity, fibril diameter, chemical fixation, hydration and fibrillar orientation. Key properties of leather, such as appearance, handle, strength, hydrothermal stability and resistance to putrefaction, are closely linked to these parameters, thereby underlining the importance of X-ray scattering to the study of leather. Recent research on the molecular level changes in collagen structure at different stages of leather processing with a range of treatments is also summarized. We will highlight how studies using X-ray scattering techniques have provided significant insights into tanning processes which could be used to improve leather properties and optimize/reduce the use of tanning agents such as chromium (III) in the industry. The review will also describe the details of collagen structure and tanning mechanisms that are yet to be determined by X-ray scattering, as well as future advancements of this technique and what it can accomplish for the leather industry.