Introduction Transforming growth factor-β1 (TGF-β1) has a crucial role in collagen synthesis and fibrosis. TGF-β1 can be antagonized and/or reduced by the action of certain agents. We propose to identify the role of decorin in treatment of tubular and interstitial fibrosis and in the inhibition of TGF-β1 in an acute ischaemic kidney. Material and methods We grouped 34 female Sprague Dawley type rats into 3 groups as 9 sham, 9 ischaemia-reperfusion (I/R) and 16 I/R + decorin respectively. The rats in the I/R + decorin group had decorin administered intraperitoneally at the dose of 0.1 mg/kg for 9 days after reperfusion. After 9 days, all the rats in the 3 groups were unilaterally nephrectomized. The TGF-β1 level was measured immunohistochemically in the nephrectomized material. Results The TGF-β1 level was lower in the I/R + decorin group. Evaluation of apoptotic activity level by caspase staining showed a statistically significant difference between the 3 groups. The number of caspase stained cells was lower in the I/R + decorin group. The amount of collagen in interstitial tissue was higher in the I/R group than in the I/R + decorin group, but this difference was not statistically significant. Conclusions We found that the TGF-β1 level – the so-called initiator of fibrotic activity – and apoptotic activity were low in the I/R + decorin group. Additional studies must be performed to understand the role of decorin in inhibition of TGF-β1 and to assess decorin’s routine use in acute renal ischaemia.