Altered expression of the microRNA-34 family has been determined to be involved in the pathogenesis of many cancers. In this review, the current knowledge of the cancer-related mechanisms in relation to the modulatory effects of microRNA-34 family were analysed. Expression analysis of the microRNA-34 family has suggested that its members play significant roles in many aspects of cancer biology including proliferation, invasion/metastasis, apoptosis/cell survival, cell cycle/cell growth, migration, senescence/aging, angiogenesis, epigenetic silencing and methylation by regulation of the expression of their target genes. Thus, microRNA-34 family members could act as prognostic markers and therapeutic targets in human cancers.