MicroRNAs (miRNAs) control gene expression and are important for the initiation and spread of cancer. By functioning as either tumor suppressive or oncogenic, miRNAs dysregulation can influence one or more cancer hallmarks, viz., angiogenesis, metastasis, apoptosis resistance, and proliferation. Circulating miRNAs also show promise as noninvasive indicators for the diagnosis and prognosis of cancer. miRNAs are being investigated as therapeutic targets due to their critical roles in gene expression. Modern techniques include the suppression of oncogenic miRNAs, miRNA replacement treatment, and sophisticated delivery systems using viral vectors and nanoparticles. miRNA-based cancer therapies are progressing due to advancements in RNA-based therapeutics, despite obstacles like the efficiency of delivery systems and their off-target effects. This chapter opens the door for precision medicine approaches in oncology by highlighting the mechanistic insights of miRNAs in cancer and their developing therapeutic potentials.