This study addresses a gap in the literature by investigating the reinforcement of mini-columns with 3D-printed lattice structures to improve the mechanical performance of cementitious materials for structural applications. Three reinforcement patterns honeycomb, re-entrant auxetic, and chiral auxetic were designed and fabricated using two additive manufacturing methods: fused deposition modeling (FDM) and digital light processing (DLP). Polylactic acid was used for FDM, and photopolymer resin for DLP printing. Each pattern was printed in both cylindrical and hyperboloid geometries and embedded into concrete mini-columns. The objective was to evaluate their influence on compressive strength, flexural behavior, and strain performance. Testing, including ultrasonic pulse velocity, was conducted to assess internal integrity. Results show that the type, placement, and geometry of the reinforcement significantly influenced mechanical performance, with DLP-printed structures providing higher resolution and improved interfacial bonding. Among the patterns, the re-entrant auxetic geometry yielded the highest enhancement in compressive strength up to 18 % compared to unreinforced samples, demonstrating the potential of auxetic designs in structural reinforcement.