Benzylisoquinoline alkaloids (BIAs) are essential secondary metabolites produced by Papaver somniferum, widely recognized for their pharmaceutical importance. This study employs transcriptome sequencing and weighted gene co-expression network analysis (WGCNA) to investigate the spatiotemporal expression patterns and regulatory networks of BIA-related genes across developmental stages and organs. A total of 23 co-expression modules were identified, revealing stage- and organ-specific dynamics in BIA biosynthesis. Key genes such as TYDC, PPO, and GsSRK demonstrated distinct regulatory roles during flowering and fruit maturation. Functional enrichment analysis uncovered critical pathways and transcription factors involved in alkaloid production. These findings enhance our understanding of the molecular regulation of BIAs and provide valuable insights for improving alkaloid yield through metabolic engineering and molecular breeding strategies.