Facial aging is primarily characterized by the loss and disorganization of the dermal extracellular matrix (ECM), particularly collagen. Injectable biostimulators, such as calcium hydroxyapatite (CaHA), represent a vital non-surgical strategy to counteract these changes by inducing neocollagenesis. This 90-day clinical trial was designed to comparatively evaluate the efficacy of a novel regenerative solution (RS) diluent, formulated to potentially enhance the biostimulatory effects of standard CaHA (STIIM product), against a conventional diluent (control) for the treatment of facial laxity. Twenty-one subjects (N = 21) were randomized to receive CaHA diluted with either RS or control formulation. Efficacy was assessed using histological analysis (collagen I area percentage), ultrasound (US) for dermal density, and clinical laxity scoring. Histological analysis, although limited by a small subsample size (N = 3), showed qualitative and exploratory evidence of collagen remodeling in both groups. However, the RS group showed enhanced dermal thickening via US (15% increase vs. 5% control, p-value = 0.012), and improvement in clinical laxity. Furthermore, histological findings, including Picrosirius red staining, indicated that the RS group resulted in qualitatively greater ECM organization and more robust type I collagen fibers compared to the control. The novel regenerative solution is safe and demonstrates enhanced neocollagenesis and clinical efficacy over the conventional formulation, validating its potential as a diluent for CaHA for optimized facial rejuvenation.