An invited contribution to a Special Collection on Synthesis and Modeling of Alloy Nanoparticles.

New multifunctional theranostic vectors allow the expansion of cancer therapeutic approaches toward scarcely investigated fields. One example is the combination of boron neutron capture therapy (BNCT) and X‐ray radiotherapy (XRT) for treating normal and XRT‐resistant hypoxic tumor regions and reduce recurrence. Of great relevance for BNCT is also the support of viable, rapid, safe, and reliable techniques for the localization and quantification of the radiosensitizers in the tissues. To address these challenges, polymer‐coated Au‐B nanoparticles (NPs) are obtained starting from a laser ablation in liquid process. Despite thermodynamic constraints, the two elements coexist by short‐range boron segregation in the gold lattice, as demonstrated experimentally and explained with the support of density functional theory calculations. Thus, the Au‐B NPs maintain a marked gold character such as biocompatibility, stability, and straightforward surface chemistry with thiolated compounds, desirable for the integration with agents capable of cell targeting and internalization. Overall, the Au‐B NPs exhibit the appropriate features for the investigation of combined BNCT and XRT, supported by the localization and quantification with X‐ray computed tomography imaging. Besides, the Au‐B nanotechnology tool is achievable without renouncing to reproducibility, environmental sustainability, and cost affordability thanks to the laser‐assisted synthetic pathway.