Cancer is one of the leading causes of death worldwide, and in many cases this is due to late detection of the disease, which complicates its treatment. MicroRNAs are short non-coding RNA sequences of ∼19-23 nucleotides that play a critical role in multiple cellular processes through post-transcriptional and translational regulation of specific genes, and an alteration in this regulatory mechanism leads to cancer. In this review, we discuss microRNA dysregulation in cancer, and propose applications of these small molecules in the treatment and diagnosis of cancer. © 2016 Sociedad Mexicana de Oncología