Background and aims <p>This study evaluated the potential of chitosan-based silicon nanoparticles (CBSNs) to reduce arsenic (As) accumulation in rice grown in As contaminated paddy soils, with a specific focus on their influence on element redistribution at the root-soil interface.</p> Methods <p>Rice was cultivated in As-contaminated soils treated with different CBSNs concentrations. As, iron (Fe), manganese (Mn), and silicon (Si) concentrations were measured in porewater, rhizosphere soil, root iron plaque (IP), and various plant tissues. Root surface elemental distribution was characterized by Scanning electron microscopy-energy dispersive spectroscopy-element mapping (SEM–EDS-mapping), and rhizosphere bacterial communities were profiled via 16S rRNA sequencing.</p> Results <p>CBSNs application reduced As uptake by rice roots by 35.27%–43.34% and decreased grain As by 36.41% (15&#xa0;mg·L⁻¹ treatment). The As content in IP increased from 2.46&#xa0;mg·kg⁻¹ in the control to 5.74&#xa0;mg·kg⁻¹ in the 15&#xa0;mg·L⁻¹ CBSNs treated group. CBSNs increased Fe/Mn on the rhizoplane, but decreased their porewater concentrations. SEM–EDS suggested enhanced Fe, Si, Mn, and As accumulation on root surfaces. These changes correlated with shifts in rhizosphere bacterial communities, including increased Proteobacteria and Firmicutes.</p> Conclusions <p>CBSNs effectively inhibited As uptake and translocation in rice, facilitated by the redistribution of As and key elements at the root interface and associated shifts in the rhizosphere microbiome. This approach presents a cost-effective and technically feasible strategy for managing As contamination in paddy soils.</p>