Previous studies showed that noncalcemic 20(OH)D3, a product of CYP11A1 action on vitamin D3, has antifibrotic activity in human dermal fibroblasts and in a bleomycin mouse model of scleroderma. In this study, we tested the role of retinoic acid-related orphan receptor γ(RORγ), which is expressed in skin, in the action of CYP11A1-derived secosteroids using murine fibroblasts isolated from the skin of wild-Type (RORγ+/+), knockout (RORγ-/-), and heterozygote (RORγ+/-) mice. CYP11A1-derived 20(OH)D3, 20,23(OH)2D3, 1,20(OH)2D3, and 1,20,23(OH)3D3 inhibited proliferation of RORγ+/+ fibroblasts in a dose-dependent manner with a similar potency to 1,25(OH)2D3. Surprisingly, this effect was reversed in RORγ+/- and RORγ-/- fibroblasts, with the most pronounced stimulatory effect seen in RORγ-/- fibroblasts. All analogs tested inhibited TGF-β1-induced collagen synthesis in RORγ+/+ fibroblasts and the expression of other fibrosis-related genes. This effect was curtailed or reversed in RORγ-/- fibroblasts. These results show that the antiproliferative and antifibrotic activities of the vitamin D hydroxy derivatives are dependent on a functional RORγ. The dramatic changes in the transcriptomes of fibroblasts of RORγ-/- versus wild-Type mice following treatment with 20(OH)D3 or 1,20(OH)2D3 provide a molecular basis to explain, at least in part, the observed phenotypic differences.