MicroRNAs (miRNAs) are short, non-coding RNA molecules that play a crucial role in regulating human gene expression by influencing messenger RNA stability and translation, thus affecting around 30% of genes post-transcriptionally. They are integral to cellular functions such as cell growth, apoptosis, and differentiation. Dysregulation of specific miRNAs has been strongly implicated in the onset and progression of several cancers, including pancreatic cancer, breast cancer, ovarian cancer, and hepatocellular carcinoma (HCC). In these malignancies, altered miRNA expression profiles contribute to tumor initiation, growth, metastasis, and resistance to therapy, highlighting their value as both biomarkers and therapeutic targets. This review synthesizes evidence on the roles of key deregulated miRNAs in these cancers, linking miRNA patterns with prognosis and responsiveness to treatment. Advances in miRNA research offer new avenues for the early detection of cancer, personalized therapy, and improved outcome prediction. By clarifying the mechanisms behind miRNA dysregulation, researchers are paving the way for novel interventions that modify miRNA activity, enhancing the precision and effectiveness of cancer treatments. The ability to specifically target aberrant miRNAs holds promise for revolutionizing clinical management, potentially improving survival rates and quality of life for cancer patients. Understanding miRNAs multifaceted roles not only deepens knowledge of cancer biology but also contributes to the development of innovative diagnostic and therapeutic strategies that can transform patient care.