<p>Laser powder bed fusion (PBF-LB/M) enables fabrication of complex, high-performance components, but reliance on pre-alloyed powder increases costs and restricts compositional flexibility. To address these challenges, in situ alloying through PBF-LB/M by mixing elemental powders provides a method that combines cost-effectiveness with customized composition and performance. In this work, Cu–4Cr–2Nb powders were prepared by resonant acoustic mixing and ball-milling, and systematically compared with pre-alloyed powder. The preparation methods caused differences in particle size distribution and laser absorptance, leading to corresponding variations in the microstructure and properties of the PBF-LB/M-fabricated components. Specifically, pre-alloyed powder showed the lowest laser absorptance, while resonant acoustic mixing powder had slightly lower absorptance than ball-milling powder. Resonant acoustic mixing powder showed superior spreadability with a lower angle of repose (29° compared to 33°), allowing a broader processing window. Samples with densities above 98.9% and uniformly distributed nano-scale precipitates were produced using all three powders. After aging treatment (500 ℃ × 2 h), the pre-alloyed sample achieved a comprehensive property combination of (803 ± 3) MPa – (12.4 ± 0.6) % - (60 ± 0.5)% IACS; the resonant acoustic mixing sample reached (790 ± 4) MPa – (11.7 ± 0.5) % - (58 ± 0.7)% IACS; and the ball-milling sample reached (765 ± 5) MPa – (11.1 ± 0.6) % - (55 ± 1.0)% IACS. These results show that, within the investigated PBF-LB/M conditions, mixed powders can achieve overall performance comparable to pre-alloyed powder. Powder mixing methods therefore significantly influence in situ alloying during PBF-LB/M. Within this laboratory-scale study, resonant acoustic mixing can be regarded as a promising route for developing advanced metal powder systems based on in situ alloying, while its scalability to industrial production will require further investigation.</p>