MicroRNAs (miRNAs) are short non-coding RNAs that modulate physiological and pathological processes by inhibiting target gene expression via blockade of protein translation or by inducing mRNA degradation. These miRNAs potentially regulate the expression of thousands of proteins. As a result, miRNAs have emerged rapidly as a major new area of biomedical research with relevance to kidney disease. MiRNA expression has been shown to differ between the kidney and other organs as well as between different kidney regions. Furthermore, miRNAs have been found to be functionally important in models of podocyte development, diabetic nephropathy and polycystic kidney disease. Of particular interest, podocyte-specific deletion of Dicer, a key enzyme in the biogenesis of miRNA, results in proteinuria and severe renal impairment in mice. One miRNA (miR-192) can also act as an effector of transforming growth factor-β activity in the high-glucose environment of diabetic nephropathy. Differential expression of miRNAs has been reported in kidney allograft rejection. It is anticipated that future studies involving miRNAs will generate new insights into the complex pathophysiology underlying various kidney diseases, generate diagnostic biomarkers and might be of value as therapeutic targets for progressive kidney diseases. The purpose of this review is to highlight key miRNA developments in kidney diseases and how this might influence the diagnosis and management of patients with kidney disease in the future.