Cancer is a deadly chronic disease and can increase quite high at this time. In general there are three ways to treat cancer, namely surgery, radiation, and chemotherapy. However, all three still have weaknesses that must be found a solution. Photodynamic Therapy/PDT is a safer for cancer treatmeant because photosensitizers with light focused on the lesion will produce singlet oxygen wich can destroy cancer cells. The photosensitizer used in this study is Magnesium Phthalocyanine (MgPc). This study aims to determine the toxicity and activity of MgPc as a photosensitizer against T47D cancer cells by PDT. Cytotoxic test without irradiation of T47D cells, PDT activity test with irradiation of T47D cells incubation time 24 hours and 48 hours. The test is used the MTT assay. In the cytotoxic test showed IC50 value of 321,753 μM. In the activity test by irradiation of T47D cells 24 hours incubation time IC50 value of 9,336 μM is higher than IC50 48 hours incubation time of 6,549 μM. MgPc compound has the potential as a photosensitizer for non-toxic PDT without irradiation and has strong toxicity to T47D cancer cells by irradiation.