This paper contributes a novel design of sensor with a heart-shaped dual-core photonic crystal fiber (PCF) to detect cancerous cells in human cervical, blood, adrenal glands, and breast. Cancer-infected cells and their normal cells are considered in liquid form having their own refractive indices. In the designed PCF, the two heart-shaped cores separated by a large circular air hole serve as two independent waveguides. The large circular air hole is infiltrated by sample cells from different body parts. Detection of cancer-contaminated cells by the proposed PCF is based on the mode-coupling theory. According to the mode-coupling theory, the guided optical light transmits periodically from one core to another, throughout the PCF length. During this transmission, the optical light interacts with the cancerous cell, which is filled in the center air hole of the PCF. Due to this interaction, the dip wavelength of the transmission spectrum is sensitive to the corresponding cancerous cell filled in the center air hole of the PCF. The variation in the PCF transmission spectrum for cancerous cells and their normal cells is observed by using the finite element method. The dip wavelength shift of the cancer cell in reference to its normal cell has been measured from the transmission spectrum to determine the sensing performance of the proposed sensor. The sensitivity achieved of the proposed sensor for cervical cancer cell, blood cancer cell, adrenal gland cancer cell, and breast cancer cells are 7916.67 nm/RIU, 8571.43 nm/RIU, 9285.71 nm/RIU, and 10,000 nm/RIU, respectively, with a maximum detection limit of 0.024. Therefore, the proposed PCF sensor suggests high sensitivity with a rapid cancer detection mechanism.