AbstractIn the advancing field of optoelectronics, multifunctional devices that integrate both detection and processing capabilities are increasingly desirable. Here, a gate‐tunable dual‐mode optoelectronic device based on a MoTe2/MoS2 van der Waals heterostructure, designed to operate as both a self‐powered photodetector and an optoelectronic synapse, is reported. The device leverages the photovoltaic effect in the MoTe2/MoS2 PN junction for self‐powered photodetection and utilizes trapping states at the SiO2/MoS2 interface to emulate synaptic behavior. Gate voltage modulation enables precise control of the device's band structure, facilitating seamless switching between these two operational modes. The photodetector mode demonstrates broadband detection and fast response speed, while the optoelectronic synapse mode exhibits robust long‐term memory characteristics, mimicking biological synaptic behavior. This dual functionality opens new possibilities for integrating neuromorphic computing into traditional optoelectronic systems, offering a potential pathway for developing advanced intelligent sensing and computing technologies.