Photoelectric pulse oximeters are widely favored for their non-invasive and continuous monitoring of pulse rate and blood oxygen saturation, which are vital indicators of physiological health. However, traditional pulse oximeters are frequently hindered by several limitations, such as high-power consumption, instability, and reduced precision. Herein, a WSe₂/Si p–n heterojunction photodiode was in-situ fabricated for self-powered high-precision pulse rate and blood oxygen saturation monitoring. Our device demonstrated the excellent broadband photoresponse performance from 265 to 980 nm, covering the biological window, including a high responsivity of 740 mA/W, a fast response time of 7.8/7.1 µs and a low detection limit of 25 nW/cm². Leveraging these prominent photoelectrical properties, the WSe₂/Si photodiode demonstrates high accuracy and reliability in detecting the physiological signals of heart rate and blood oxygen saturation through a triple-wavelength measurement method, with an error margin of less than 1%, thereby validating its accuracy and reliability for non-invasive health monitoring applications. These achievements provide a new approach for developing low-power, high-sensitivity optoelectronic pulse oximeters.