Octamer-binding transcription factor 4 (OCT4) belongs to the POU-homeodomain family of transcription factors and binds to an octamer motif, ATGCAAAT. OCT4 is the key transcription factor that is involved in the maintenance of pluripotency and self-renewal in undifferentiated embryonic stem (ES) cells. OCT4 has been reported to be overexpressed in various cancers including lung, germ cell tumors, breast, cervix, prostate, gastric, liver, and ovarian cancer. MicroRNAs (miRNAs), small non-coding RNAs, modulate mRNA expression through base pairing between seed sequences in miRNA and complementary sequences of the target mRNA, thereby destabilizing mRNA and/or inhibiting protein synthesis. Several miRNAs have been demonstrated to regulate stemness factors such as OCT4, NANOG, SOX2 and KLF4 in cancer cells, thereby modulating the proliferation, apoptosis, differentiation, drug resistance and immunity of cancer cells.