MicroRNAs (miRNAs) are small, non-coding RNAs (18-25 nucleotides) that post-transcriptionally modulategene expression by negatively regulating the stability or translational efficiency of their target mRNAs. In thiscontext, the present study aimed to evaluate the in vitro effects of miR-153 inhibition in the breast carcinomacell line MDA-MB-231. Forty-eight hours after MDA-MB-231 cells were transfected with the miR-153 inhibitor,an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was utilized to determine theeffects of miR-153 on cell viability. Flow cytometry analysis and assessment of caspase 3/7 activity were adoptedto determine whether miR-153 affects the proliferation rates and apoptosis levels of MDA-MB-231 cells. Ourresults showed that silencing of miR-153 significantly inhibited growth when compared to controls at 48 hours,reducing proliferation by 37.6%, and inducing apoptosis. Further studies are necessary to corroborate ourfindings and examine the potential use of this microRNA in future diagnostic and therapeutic interventions.