This study identifies Sugar Transporter Protein 28 (OsSTP28) as a key regulator of nitrogen (N)-responsive tillering and yield formation in rice. Increased N supply inhibits *OsSTP28* expression, leading to glucose accumulation in tiller buds. This suppresses the transcriptional inhibitor *OSH15* via an epigenetic mechanism, activating gibberellin catabolism and promoting tillering and yield. An elite *OsSTP28* allele enhances this response, offering a valuable breeding target for improved N use efficiency.