Introduction: Cercis siliquastrum (Judas tree) is a traditional medicine with drug discovery potential. The aim of this study was to investigate the antimicrobial and antioxidant activity of Cercis siliquastrum L. flowers and leaves for their effect on the DNA cell cycle (proliferation) in a breast cancer cell line. Methods: Assessment of the DNA cell cycle of breast cancer was conducted using propidiumiodide (PI) while apoptosis activity was estimated by staining with Annexin-V using flow cytometry. The antimicrobial activity was assessed through a broth microdilution method on four bacterial pathogens and one fungal strain. Moreover, the Diphenylpicrylhydrazyl (DPPH) method was utilized to evaluate free radical scavenging efficacy of C. siliquastrum flowers and leaves in four different solvent fractions. Results: The acetone and methanol fractions of C. siliquastrum leaves and flowers showed highest antioxidant potentials with IC50 values of 8.31 ± 1.36, 4.78 ± 1.84, 1.75 ± 2.03 and 3.31 ± 1.66 μg/ml, respectively compared with Trolox that had an antioxidant potential of IC50 value of 1.41 ± 1.05 μg/ml. The leaf hexane fraction showed potent antibacterial potential versus Staphylococcus aureus, Methicillin-Resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa with MIC values of 0.007, 0.024, 0.048 mg/ml, respectively. Notably, the C. siliquastrum flowers hexane fraction strongly inhibited growth of Staphylococcus aureus, Pseudomonas aeruginosa, MRSA, and Candida albicans with MIC values of 0.009, 0.039, 0.048 and 0.08 mg/ml, respectively. Moreover, C. siliquastrum leaves and flowers hexane fractions caused cell cycle arrest followed by cell death via apoptosis/necrosis due predominantly to defects in the mitotic process. Conclusion: Our data revealed the significant antimicrobial and antioxidant effects of C. siliquastrum that contributed significantly to the cytotoxicity of cancer cells requires further detailed studies.