In recent years, mycophenolate mofetil (MMF)–based immunosuppressive regimen was recommended in induction and in maintenance therapy in lupus nephritis (LN), one of the most severe and common manifestations of systemic lupus erythematosus. However, no recommendations were made so far regarding monitoring of mycophenolic acid (MPA) plasma concentrations. Therapeutic drug monitoring (TDM) constitutes a practical tool to ensure optimal posology. In renal transplantation, it was proved that acute allograft rejection incidences decreased when the recommended MPA target exposure has been maintained (30–60 mg·h·L−1). The results obtained in the field of transplant medicine indicate the potential benefit of carrying out TDM in LN. To date, the correlation of MPA exposure and clinical outcomes in the population of LN patients was the objective of just a few studies. The aim of this review was therefore to present TDM studies in LN patients on MMF therapy and to compare their results. Based on the conclusions drawn from TDM studies in LN, it can be suggested that the area under the concentration–time curve threshold values of 30–45 mg·h·L−1 can potentially be associated with favorable treatment outcome. Moreover, the majority of the analyzed studies indicate relatively good correlation between trough concentration and the area under the concentration–time curve in patients treated with MMF that constitutes an important implication for TDM approach in routine setting. The threshold of 3 mg/L can potentially be recommended as a target trough value.