Abstract Background Breast cancer ranks as the foremost cause of cancer-related mortality among women globally. Timely diagnosis stands as the most effective approach in mitigating breast cancer mortality rates. There exists a close relationship between immune processes and tumorigenesis. This study aims to elucidate the immune mechanisms and potential biomarkers associated with breast cancer using bioinformatics techniques. Objective Initially, differentially expressed genes were identified through consensus analysis of invasive breast cancer (BRCA) samples sourced from The Cancer Genome Atlas (TCGA) database, focusing on immunotherapy response. Subsequently, protein–protein interaction (PPI) networks, Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were employed to refine the selection of potential genes. Lastly, expression and prognostic analyses of hub genes were conducted to identify reliable key genes, with a focus on CCL19. Immunohistochemistry (IHC) was employed to assess the differential expression of CCL19 in both tumor and adjacent breast tissue samples. Additionally, protein correlation analysis, signaling pathway analysis, immune infiltration analysis, gene co-expression analysis, and drug sensitivity analysis of CCL19 were conducted to investigate its pathological clinical features and potential biological functions. Results CCL19 expression exhibited a significant increase in breast cancer. Elevated CCL19 expression correlates with advanced tumor stage and indicates a favorable prognosis in breast cancer. CCL19 expression correlates with the abundance of diverse tumor-infiltrating immune cells (TIICs). CCL19 exhibits a positive correlation with the expression of the majority of immune-related genes. Enrichment analysis revealed the involvement of CCL19 in immune-related pathways and the PI3K-Akt signaling pathway. These findings suggest that CCL19 may influence breast cancer prognosis through immune infiltration. Patients exhibiting high CCL19 expression demonstrated more favorable responses to immunotherapy. Conclusion Breast cancer demonstrates overexpression of CCL19. CCL19 holds promise as a biomarker for forecasting breast cancer prognosis and as a potential therapeutic target.