Neauvia Stimulate® is a biocompatible, injectable hyaluronic acid (HA) filler (26 mg/ml) PEG cross-linked with 1% of calcium hydroxyapatite (CaHA) for facial soft-tissue augmentation that provides volume to tissues, followed by a process of neocollagenesis for improving skin quality. The aim of the present study is to evaluate the possible modulation of collagen synthesis after treating human fibroblasts cultured in vitro with the product (Lot. 160517-26-1/2 PEG). The experimental model proposed, despite being an in vitro system, allows the derivation of useful information to predict the possible activity of the product in further in vivo application. Human fibroblasts (PEU cells) were treated with the product for 24 h at increasing concentrations of compared to control (untreated cells). The modulation of collagen synthesis was evaluated using a specific colorimetric kit (Sircol, Soluble Collagen Assay Kit). Increment of collagen production, 37.62% and 97.39% at concentrations of 1.25 mg/ml and 2.5 mg/ml of product, respectively, was considered to be statistically significant (*p values≤0.05 and **p values≤0.01) when compared with control (untreated cells). In conclusion, Hyaluronic Acid Hydrogel 26 mg/ml PEG cross-linked with calcium hydroxyapatite in low concentrations (1%) determines a statistical increment in neocollagenesis.