Abstract: Boron Neutron Capture Therapy (BNCT) is a binary targeted radiotherapeutic approach that achieves single-cell-level tumor eradication via the ¹⁰B(n,α)⁷Li nuclear reaction, thereby offering distinct clinical advantages for recurrent and refractory solid tumors. The performance of boron delivery agents is a pivotal factor governing both the therapeutic efficacy and safety of BNCT. Conventional boron agents are inherently constrained by inadequate tumor specificity, low boron payload, suboptimal pharmacokinetic behavior, and the absence of real-time imaging capabilities, which collectively undermine their clinical applicability in precision nuclear medicine. To overcome these shortcomings, the modular design strategy has recently been introduced into BNCT boron drug development, culminating in an integrated platform that encompasses four functional modules: targeted recognition, high-density boron loading, intelligent delivery, and multimodal imaging. This conceptual shift is progressively steering BNCT boron agents toward advanced systems featuring active tumor targeting, smart controlled release, and theranostic integration. The present review systematically examines the research landscape and key technological breakthroughs in modular BNCT boron drugs over the period from 2020 to 2026. It elucidates the design principles and optimization strategies for each individual module, with special emphasis on the scientific challenges inherent in multi-module synergistic assembly. Future perspectives are also delineated, highlighting intelligent responsive multimodal boron formulations, device-drug integrated precision theranostic systems, and cost-effective domestically manufactured solutions, with the goal of furnishing a systematic reference framework for the molecular design, process refinement, quality assurance, and clinical translation of next-generation BNCT boron agents.