Human serum albumin (HSA) is the most abundant circulating plasma protein. Besides a significant contribution to the osmotic pressure, it is also involved in the fine regulation of many other physiological processes, including the balance of the redox state, the inflammatory and/or immunological responses, and the pharmacokinetic and pharmacodynamics of many drugs. Growing evidence suggests that HSA undergoes structural and functional damage in diseases characterized by an enhanced systemic inflammatory response and oxidative stress, as it occurs in chronic liver disease. Based on their clinical relevance, this review provides a summary of the most common post-translational modifications affecting HSA structural integrity and functions and their clinical relevance in the field of liver disease. The review also provides a critical description of the analytical approaches employed for the investigation of conformational alterations and the identification/quantitation of specific post-translational modifications affecting HSA. Finally, the analytical methods available for the assessment of two of the most clinically relevant non-oncotic properties of HSA, namely the binding capacity and the antioxidant activity, are critically reviewed. Among the available techniques particular attention is given to those proposed for the in vitro and in vivo investigation of structurally modified albumin.