MicroRNAs (miRNAs) are single-stranded non-coding endogenous RNAs linked with normal developmental and physiological processes. Recent studies have demonstrated that the dysregulation of miRNAs plays an important role in the beginning, progression, and metastasis of many cancers. Additionally, they are involved in the regulation of the epithelial-to-mesenchymal transition (EMT) in many cancer cells. Several studies have suggested that phytochemicals play an important role in the modulation of miRNA expression, which is related to changes in oncogenes, tumour suppressors, and cancer-related protein expression. Hence, phytonutrients can suppress tumour development, prevent metastasis, reverse the EMT, and improve drug sensitivity via the modulation of miRNA expression. In this review, we discuss tumour-suppressing and oncogenic miRNAs and the mechanism of action for miRNAs as well as the role of phytochemicals in the modulation of miRNAs in various cancer cells.