Objective To investigate the expression and clinical significance of CD97 and its ligand CD55 in triple negative breast cancer (TNBC). Methods The expression of CD97 and CD55 in 70 TNBC tissues and 50 normal tissues were detected by immunohistochemistry. Results The expression level of CD97 in TNBC tissue was significantly higher than that in normal breast tissue (P < 0.05), and its expression was correlated with lymph node metastasis, tumor stages, vascular thrombus, tumor sizes and ki-67 expression in TNBC tissue (P < 0.05). The expression level of CD55 in TNBC tissue was significantly higher than that in normal breast tissue (P < 0.05), and its expression was correlated with lymph node metastasis, tumor stages, vascular thrombus, tumor sizes and ki-67 expression in TNBC tissue (P < 0.05). There was a positive correlation between CD97 and CD55 expression in TNBC (P < 0.05). Conclusions CD97 and CD55 may be involved in the occurrence and development of TNBC, play a role in the progression of TNBC and may become new tumor markers.