The incidence of diabetes is escalating worldwide and, consequently, this has become a major health care problem. Moreover, both type 1 and type 2 diabetes are associated with significantly accelerated rates of microvascular complications, including retinopathy, nephropathy, and neuropathy, as well as macrovascular complications such as atherosclerotic cardiovascular and hypertensive diseases. Key factors have been implicated in leading to these complications, including hyperglycemia, insulin resistance, dyslipidemia, advanced glycation end products, growth factors, inflammatory cytokines/chemokines, and related increases in cellular oxidant stress (including mitochondrial) and endoplasmic reticulum stress. However, the molecular mechanisms underlying the high incidence of diabetic complications, which often progress despite glycemic control, are still not fully understood. MicroRNAs (miRNAs) are short noncoding RNAs that have elicited immense interest in recent years. They repress target gene expression via posttranscriptional mechanisms and have diverse cellular and biological functions. Herein, we discuss the role of miRNAs in the pathobiology of various diabetic complications, their involvement in oxidant stress, and also the potential use of differentially expressed miRNAs as novel diagnostic biomarkers and therapeutic targets.