This study aimed to develop a novel antibacterial photocurable resin for vat-photopolymerization (VPP) 3D printing by incorporating cetylpyridinium chloride (CPC) and to comprehensively evaluate its printability, mechanical properties, antibacterial activities, and CPC-release behavior for potential use in dental prostheses and orthodontic devices. Photocurable resins containing 0–3 wt% CPC were formulated from methacrylate and acrylate monomers. Printability of the photocurable resins was assessed by measuring viscosity, cure depth, over-curing, and degree of conversion. The photocurable resins were printed using a VPP 3D printer, and the resulting printed specimens were evaluated for mechanical properties using three-point bending and Vickers hardness tests. Antibacterial activity against Streptococcus mutans was examined by bacterial viability and plaque-formation assays. CPC-release behavior was analyzed by UV-Vis spectroscopy. CPC incorporation up to 3% slightly increased resin viscosity, cure depth, and over-curing while maintaining adequate printability. The degree of conversion was not significantly affected by CPC content. The 1% CPC-loaded printed resin exhibited mechanical properties comparable to the CPC-free control, whereas 3% CPC markedly reduced them. The 1% CPC-loaded printed resin showed strong antibacterial activity, achieving an antibacterial activity value (R) of 5.6 (>99.99% bacterial reduction), and demonstrated sustained plaque inhibition. Continuous CPC release from the printed resins was confirmed throughout the 14-day evaluation period. These results demonstrate that 1% CPC-loading provides an optimal balance among printability, mechanical properties, and antibacterial performance. The developed material shows potential for application in 3D-printed dental polymer-based prostheses and orthodontic devices.