We summarized the results of the regulatory interactions of twenty-five microRNAs with FOXO3a in five types of malignant tumours and found that dual microRNAs synergize with FOXO3a to inhibit breast cancer cell growth including two groups; Three individual microRNAs collaborated with FOXO3a to restrain hepatocellular carcinoma progression; Twelve individual microRNAs antagonized FOXO3a to promote the development of a single tumour cell, respectively; and five microRNAs antagonized FOXO3a to contribute to the progression of more than two types of tumours. The gene discussed is FOXO3; the disease is breast cancer.