Liver cirrhosis, which is considered one of the leading causes of death in the world, can lead to severe complications, and is often followed by a liver transplantation. These patients take an average of nine medications daily. If not managed adequately, it can be accompanied by serious drug-related problems. To reduce this risk, a clinical pharmacist may be included as part of the healthcare team to optimize medication therapy in this population. This study aimed to systematically identify the pharmaceutical interventions which reduced drug-related problems and improved medication therapy for adult hospitalized liver cirrhotic and liver transplant patients when compared to standard care. Three databases (PubMed, Embase, and CENTRAL) were systematically searched from the inception of each database to 25 October 2023, and interventional studies in the English language were included. The risk of bias was assessed according to RoB-I for the UBA study and RoB2 for the identified RCT. The detected interventions to reduce drug-related problems in liver cirrhotic and liver transplant patients were extracted and classified according to a “Hierarchy of Controls” model. Two studies from Germany and the USA met our inclusion criteria, respectively. In these studies, we identified two interventions that included education, expert consultation, and the monitoring of the immunosuppressive medications serum level. The main objective of the two included studies was improving patients’ compliance through adherence. These pharmaceutical interventions identified were classified as administrative controls, which is one of the lowest levels in the “Hierarchy of Controls” with which to address a potential risk. Pharmaceutical interventions to optimize medication therapy were found to be rare in the examined population, and were limited to “administrative controls”. These interventions were limited to transplant patients’ education and the monitoring of the immunosuppressive medication serum levels. No interventional studies were found to have investigated pharmaceutical interventions in patients with liver cirrhosis. Especially regarding this patient group, future studies to reduce DRPs using pharmaceutical interventions are needed. This study received no external funding and its PROSPERO registration number is CRD42022309122.