Background: Breast cancer is cancer with the second-largest prevalence in the world. Conventional cancer treatments such as surgery, chemotherapy, and radiotherapy are known to have drawbacks and side effects to normal cells, thus a cancer treatment method that has low side effects on normal cells is needed. Photodynamic Therapy (PDT) is an alternative method that is more selective against cancer cells and safer against normal cells. There are 3 basic components in PDT, namely light, photosensitizer (PS), and oxygen, which when all three are combined will cause cell and tissue death. The ideal PS compound that can be used in PDT should have low toxicity in the dark but have high anticancer activity when exposed to light at certain wavelengths. The PS compound used in this study was Fe (II) Phthalocyanine (Fe(II)Pc). Method: The method used in this research was the MTT assay based on the colorimetric method. Breast cancer cells (T47D) were treated with Fe(II)Pc at various concentration levels, then the cell absorbance was measured using an ELISA reader. The absorbance value of the cells obtained was then used to measure the % value of cell viability and the IC50 value. The results obtained were then compared with the control group cells that were not treated with Fe(II)Pc. In this study, two tests were carried out, namely the cytotoxic test without irradiation (dark toxicity) and the PDT activity test with 24 and 48 hours incubation. Results: The results of the dark toxicity test obtained an IC50 value of 397.729 ± 0.9 μM, while the results of the PDT activity test with 24 hours and 48 hours incubation obtained IC50 values of 84.738 ± 0.796 μM and 52.319 ± 0.827 μM. Conclusion: Fe(II)Pc has very low dark toxicity, thus it appears that Fe(II)Pc is safe against normal cells. In addition, Fe(II)Pc has low anticancer activity against breast cancer cells (T47D) after the PDT test is carried out, which indicates that Fe(II)Pc has low potential to be used as PS in PDT.