Mitochondria are critical regulators of cell metabolism; thus, mitochondrial dysfunction is associated with many metabolic disorders, including cancer. Altered metabolism is a common property of cancer cells that exhibit enhanced capacity to 'ferment' glucose to pyruvate and then lactate, even in the presence of sufficient oxygen to support mitochondrial metabolism. Recently, it was reported that microRNAs (miRNAs) regulate important signalling pathways in mitochondria and many of these miRNAs are deregulated in various cancers. Different regulatory mechanisms can control miRNA expression at the genetic or epigenetic level, thus affecting the biogenetic machinery via recruitment of specific transcription factors. Metabolic reprogramming that cancer cells undergo during tumorigenesis offers a wide range of potential targets to impair tumour progression. MiRNAs participate in controlling cancer cell metabolism by regulating the expression of genes whose protein products either directly regulate metabolic machinery or indirectly modulate the expression of metabolic enzymes, serving as master regulators. Thus, modulation of the level of miRNAs may provide a new approach for the treatment of neoplastic diseases.