Background: Photodynamic therapy is an alternative anticancer treatment approach that promises high therapeutic efficacy. In this study, it is aimed to investigate the PDT-mediated anticancer effects of newly synthesized silicon phthalocyanine (SiPc) molecules on MDA-MB-231, MCF-7 breast cancer cell lines, and non-tumorigenic MCF-10A breast cell line. Methods: Novel bromo substituted Schiff base (3a), its nitro homolog (3b), and their silicon complexes (SiPc-5a and SiPc-5b) were synthesized. Their proposed structures were confirmed by FT-IR, NMR, UV–vis and MS instrumental techniques. MDA-MB-231, MCF-7 and MCF-10A cells were illuminated at a light wavelength of 680 nm for 10 min, giving a total irradiation dose of 10 j/cm2. MTT assay was used to determine the cytotoxic effects of SiPc-5a and SiPc-5b. Apoptotic cell death was analyzed using flow cytometry. Changes in the mitochondrial membrane potential were determined by TMRE staining. Intracellular ROS generation was observed microscopically using H2DCFDA dye. Colony formation assay and in vitro scratch assay were performed to analyze the clonogenic activity and cell motility. Transwell migration and matrigel invasion analyzes were conducted to observe changes in the migration and invasion status of the cells. Results: The combination of SiPc-5a and SiPc-5b with PDT exhibited cytotoxic effects on cancer cells and triggered cell death. SiPc-5a/PDT and SiPc-5b/PDT decreased mitochondrial membrane potential and increased intracellular ROS production. Statistically significant changes were detected in cancer cells' colony-forming ability and motility. SiPc-5a/PDT and SiPc-5b/PDT reduced cancer cells' migration and invasion capacities. Conclusion: The present study identifies PDT-mediated antiproliferative, apoptotic, and anti-migratory characteristics of novel SiPc molecules. The outcomes of this study emphasize the anticancer properties of these molecules and suggest that they may be evaluated as drug-candidate molecules for therapeutic purposes.