Complexes [Pd(bipy)(mtzt)2] (1) and [Pd(5,6-dmphen)(mtzt)2] (2) (where Hmtzt, bipy and 5,6-dmphen are 1-methyl-1H-1,2,3,4-tetrazole-5-thiol, 2,2′-bipyridine and 5,6-dimethyl-1,10-phenanthroline, respectively) were synthesized by the reaction of a mixture of Hmtzt and 2,2′-bipyridine (1) or 5,6-dimethyl-1,10-phenanthroline (2) with Pd(II) chloride. Complexes 1 and 2 were fully characterized by elemental analysis, 1H NMR, IR, UV–Vis, luminescence spectroscopy as well as single-crystal X-ray diffraction method. According to single-crystal X-ray diffraction, central Pd(II) ions in 1 and 2 have a slightly distorted square-planar geometry, involving the S atoms from two mptrz− ligands and two nitrogen atoms from bipy (complex 1) and 5,6-dmphen (complex 2) ligands (τ4 = 0.09 for 1 and 0.07 for 2). Additionally, some well-known non-covalent intermolecular interactions such as hydrogen bonding (complexes 1 and 2), π–π (complexes 1 and 2), and ring-metal interactions (complex 2) have also been involved in these complexes. These kinds of interactions have been observed to be responsible for the formation of the 3D supramolecular structure. The luminescence properties of the free ligand, as well as the complexes 1 and 2, were investigated in solution. The interaction of the complexes with DNA was investigated by UV–Vis absorption spectra. The results indicate that complexes bind to DNA and the intrinsic binding constant (Kb) of complexes 1 and 2 were about 2.19 × 105 and 1.51 × 105 M−1, respectively. Gel electrophoresis assay demonstrates the ability of the complexes to bind the plasmid DNA. The anti-tumor properties of Pd(II) complexes were evaluated as in vitro anti-proliferative activity by MTT assay in human breast cancer cell lines (MCF-7, SKBR-3, and MDA-MB-231). It suggests that complex 2 might dedicate important anti-tumor properties and 5,6-dmphen ligand has an important effect on cytotoxicity, so complex 2 shows IC50 value in μM range as effective as cisplatin.