This study demonstrates a design strategy for 3D printing high-strength, high-conductivity copper (Cu) using laser powder bed fusion (L-PBF). By uniformly dispersing a minor portion of lanthanum hexaboride (LaB6) nanoparticles in pure Cu, the researchers achieve improved processability, strength, thermal stability, and conductivity. The addition of LaB6 enhances the yield strength to 347 ± 2 MPa, elongation to failure to 22.8 ± 1.2%, electrical conductivity to 98.4% IACS, and thermal conductivity to 387 W m−1 K−1. The strategy also allows for the fabrication of geometrically complex components with high density and performance. The 1.0 wt% LaB6-Cu exhibits superior mechanical and electrical properties compared to conventional and additively manufactured Cu, Cu alloys, and Cu matrix composites, making it suitable for applications requiring high strength, conductivity, and thermal stability.This study demonstrates a design strategy for 3D printing high-strength, high-conductivity copper (Cu) using laser powder bed fusion (L-PBF). By uniformly dispersing a minor portion of lanthanum hexaboride (LaB6) nanoparticles in pure Cu, the researchers achieve improved processability, strength, thermal stability, and conductivity. The addition of LaB6 enhances the yield strength to 347 ± 2 MPa, elongation to failure to 22.8 ± 1.2%, electrical conductivity to 98.4% IACS, and thermal conductivity to 387 W m−1 K−1. The strategy also allows for the fabrication of geometrically complex components with high density and performance. The 1.0 wt% LaB6-Cu exhibits superior mechanical and electrical properties compared to conventional and additively manufactured Cu, Cu alloys, and Cu matrix composites, making it suitable for applications requiring high strength, conductivity, and thermal stability.