Skin ageing is an inevitable process characterized by loss of elasticity and decreased dermal volume. Nanofat injection is a new technique used for long-lasting skin rejuvenation, while hyaluronic acid (HA) is widely used to improve skin rejuvenation temporarily. This work aimed to compare the effect of nanofat versus hyaluronic acid (HA) subcutaneous injections on the aged thin skin of female rats. Four equal groups of 40 female rats were included in this study. Group I (GpI) was the control adult, while GpII was the control aged one. GpIII aged rats received a single subcutaneous (SC) injection of 0.1 ml of cross-linked HA, while Gp IV-aged rats received a single SC injection of 0.1 ml of nanofat. Light microscopic examination was done following staining with H&E, Masson trichrome, and anti-vascular endothelial growth factor (VEGF) immunostaining, in addition to electron microscopic study. The light and electron microscopic examination of GpIII and GpIV revealed structural rejuvenation of their aged skin. In the papillary dermis, collagen fibers were fine, interlocking small bundles. In the reticular dermis, they appeared as thick, closely packed bundles, with elastic fibers and active fibroblasts in between. Morphometric analysis displayed a significant increase in the mean total thickness of the dermis, mean area percentage of Masson trichrome-stained collagen fibers, and mean number of positive VEGF blood vessels of both GpIII and GpIV compared to group II. In conclusion, nanofat and HA subcutaneous injections improved skin ageing signs; however, nanofat injection is particularly predominant in neovascularisation and collagen formation.