Diabetic nephropathy (DN) is a major microvascular complication of diabetes characterized by increasing albuminuria and progressive loss of kidney function. Increased excretion of albumin into the urine is a key feature of DN, and its assessment is considered to be an early marker predicting the onset and progression of DN. However, albuminuria has certain limitations; therefore, the quest for more reliable renal biomarkers with higher sensitivity and specificity are needed for early prediction of the onset and monitoring of the progression of DN. Furthermore, such biomarkers may also provide a better insight into identifying the complex pathophysiological processes responsible for DN. This article aims to provide a comprehensive and critical review of the current literature on relevant biomarkers of kidney injury, including markers of renal fibrosis, inflammation, and oxidative stress, as well as addressing contemporary proteomic approaches.