Backgroud: The purpose of this study was to elucidate the regulation of programmed death ligand 1 (PDL1), lactate dehydrogenase A (LDHA) and miR-34a in triple negative breast cancer (TNBC) and to explore the function and mechanism of PDL1 and LDHA as competitive endogenous RNAs (ceRNAs) in TNBC via regulation of miR-34a. Methods: Western blotting, quantitative RT-PCR (qRT-PCR) and immunohistochemistry (IHC) assays were conducted to explore the expression of PDL1, LDHA and miR-34a in TNBC and correlations between them. MTS cell viability, Transwell migration, glucose consumption and lactate production assays and flow cytometry were performed and mouse xenograft models were constructed to explore the functions and regulation of the PDL1 3'UTR and LDHA 3' UTR and miR-34a in TNBC. Results: We found that PDL1 and LDHA were synchronously upregulated in TNBC cell lines and tissues. Co-expression of PDL1 and LDHA was correlated with poor outcome in TNBC. Both PDL1 and LDHA are targets of miR34a, and the 3' UTRs of PDL1 and LDHA both have binding sites for miR-34a. The functions of PDL1 and LDHA were inhibited by miR-34a. In addition, PDL1 and LDHA acted as ceRNAs to promote the expression and function of each other through regulation of miR-34a in TNBC. Conclusions: This study provides a new theoretical basis for a novel TNBC therapeutic strategy. Simultaneously targeting PDL1 and LDHA, which would combine immunotherapy and metabolically targeted treatments, might shed some light on the treatment of breast cancer, especially TNBC.