MicroRNAs (miRNAs) are small non-coding RNAs that function by base pairing with messenger RNAs, thereby regulating protein expression. Functional studies indicate that miRNAs are involved in the regulation of almost every biological pathway. Moreover, changes in miRNA expression are associated with several human pathologies, including cancer. Dysregulation and aberrant expression of microRNA-100 (miR-100) have been reported to be involved in tumorigenesis and tumor progression of several cancer types, suggesting that miR-100 might serve as a diagnostic and/or prognostic marker for human malignancy. In this review, we summarize the potential application of miR-100 in cancer treatment and as a new molecular marker for cancer prognosis and diagnosis. We will provide a brief introduction to miR-100 and discuss its role as a non-invasive biomarker and a potential therapeutic target in human cancers.