Background: Cancer has become a major cause of death today. These risk factors are also balanced with the development of drugs, one of which comes from nature. Medical products derived from natural resources such as blood clam (Anadara (tegillarca) granosa) have been already developed. Crude protein extracted from blood calm contains a 20-kDa protein which had been known to be able to inhibit the growth of HT-29 cell line. Purpose: This study aimed to determine cytotoxic activity and apoptotic effect of crude protein which is isolated from blood calm against breast cancer T47d cell line. Materials and Methods: This study used the ammonium sulfate precipitation method for the isolation of a crude protein of blood clams. MTT assay method was performed to determine cytotoxicity and to know the value of IC50, apoptosis test qualitatively and quantitatively was done by double-staining using ethidium bromide and acridine orange as well as flow cytometric dye using annexin V dyes and propidium iodide. Findings: Crude protein clams of blood have IC50 value of 11.11μg/ml and can induce apoptosis of breast cancer cell line (T47D) at 15 μg/ml concentration by double-staining method, but the calculation with flow cytometry method still shows different results in this study. Research Limitations: This study observed the inhibitory concentration of crude extract consisting of proteins with various molecular weights against the t47d cell line. Originality: The results of this study indicate that crude protein clams are cytotoxic and can induce apoptosis in breast cancer cell lines (T47D).