Background: Cancer is a characterized disease by the growth of abnormal cells in body tissues where the death rate from cancer is estimated to reach 23.6 million. Breast cancer ranks first with a frequency of 18.6% of cancer cases that occur in Indonesia. Photodynamic Therapy / PDT is a safer alternative to cancer treatment. This therapy is a special therapy that combines light, oxygen, and certain light-sensitive compounds (photosensitizers). Light stimulates photosensitization compounds, which produce the formation of reactive oxygen (Reactive Oxygen Spesies /ROS) which can destroy tumors selectively. The photosensitizer used in this study was Copper Phthalocyanine (CuPc). This study aims to determine the toxicity and activity of CuPc as a photosensitizer against T47D cancer cells by PDT. Method: Cytotoxic test was carried out without irradiation of T47D cells, PDT activity test was carried out irradiation of T47D cells at 2 different incubation times 24 hours and 48 hours. The test method used MTT assay method. Results: The cytotoxic test without exposure showed IC50 value of 241.19 μM with value SD = ± 1,48. In the activity test by irradiation of T47D cells 24-hour incubation time IC50 value of 9.92 μM higher than IC50 48-hour incubation time of 6.42 μM with consecutive SD value are ± 1,38 and ± 1,06. The CuPc compound has potential as a photosensitizer for PDT which, without irradiation is non-toxic while has strong toxicity to T47D cancer cells in the presence of radiation.