Macrophages are highly plastic cells with the ability to differentiate into both M1- and M2-polarized phenotypes. As a distinct M2-polarized population, tumour-associated macrophages (TAMs) promote tumorigenesis owing to their pro-angiogenic and immune-suppressive functions in tumour microenvironment. In the present study, we found that the microRNA-720 (miR-720) was down-regulated in TAMs isolated from breast carcinomas and M2-polarization macrophages. Overexpression of miR-720 attenuated M2 phenotype expression and thus inhibited M2 polarization. We further identified GATA binding protein 3 (GATA3), a transcriptional factor that plays an important role in M2 macrophage polarization, was the downstream target of miR-720 Ectopic expression of GATA3 restored the M2 phenotype in miR-720 overexpressed macrophages. Importantly, overexpression of miR-720 inhibited pro-migration behaviour and phagocytic ability of M2-polarized macrophages. Thus, our data suggest that miR-720 plays an important role in regulating M2 macrophage polarization and function.