The present study assessed whether microRNA (miR)‑27a is an influential factor in steroid‑induced osteonecrosis of the femoral head (ONFH) and investigated the underlying mechanism of action. The results indicated that serum miR‑27a was decreased in a rat model of ONFH compared with that in control rats. It was also observed that increased miR‑27a expression promoted osteogenic differentiation and cell proliferation, inhibited caspase‑3/9 and B‑cell lymphoma‑2‑associated X protein expression and induced alkaline phosphatase (ALP) activity and bone morphogenetic protein (BMP)‑2, runt‑related transcription factor (Runx)2 and osteonectin mRNA expression in osteoblastic MC3T3‑E1 cells. miR‑27a mimics also induced transforming growth factor (TGF)‑β and Smad7 protein expression in MC3T3‑E1 cells. Furthermore, transfection with TGF‑β expression plasmid was able to enhance the effects of miR‑27a mimics on osteoblastic differentiation, cell proliferation, ALP activity, BMP‑2, Runx2 and osteonectin mRNA expression, and Smad7 protein expression in the MC3T3‑E1 cells. Transfection with a TGF‑β or Smad7 expression plasmid also enhanced the effects of miR‑27a mimics on osteoblastic differentiation, cell proliferation, ALP activity and osteonectin mRNA expression in the MC3T3‑E1 cells. Taken together, the results of the present study suggested that the induction of TGF‑β/Smad7 signaling in osteoblasts may be a potential mechanism by which miR‑27a regulates steroid‑induced ONFH.