Plastics are widely used across various industries due to their light weight, durability, and low cost. However, their extensive use has led to environmental contamination, with microplastics and nanoplastics (NPs) becoming emerging pollutants of global concern. These particles can enter the food chain and pose significant threats to food safety and human health. While numerous studies have examined the accumulation, translocation, and toxicity of nanoplastics in herbaceous crops, their potential impact on woody nut-producing species remains largely unexplored. In this study, we investigated the effects of NPs on the nuts of Torreya grandis, a commercially and nutritionally important tree species. Our preliminary results demonstrated that exogenously applied NPs could penetrate the nut tissue and accumulate internally. This accumulation significantly reduced nut size and led to a notable change in key nutritional components, including sucrose and oils. Transcriptome analysis revealed that nut size reduction was associated with alterations in multiple metabolic and signaling pathways. In particular, genes involved in sucrose biosynthesis were significantly downregulated following NP exposure, suggesting a direct link between nanoplastic stress and impaired carbon metabolism. In summary, this study provides novel insights into the adverse effects of NPs on nut development and nutritional quality in T. grandis, and highlights the potential ecological and food safety risks posed by nanoplastic contamination in perennial nut crops.