Tremendous efforts have been devoted to preparing the ultrathin two‐dimensional (2D) transition‐metal dichalcogenides (TMDCs) and TMDCs‐based heterojunctions owing to their unique properties and great potential applications in next generation electronics and optoelectronics over the past decade. However, to fulfill the demands for practical applications, the batch production of 2D TMDCs with high quality and large area at the mild conditions is still a challenge. This feature article reviews the state‐of‐the‐art research progresses that focus on the preparation and the applications in electronics and optoelectronics of 2D TMDCs and their van der Waals heterojunctions. First, the preparation methods including chemical and physical vapor deposition growth are comprehensively outlined. Then, recent progress on the application of fabricated 2D TMDCs‐based materials is revealed with particular attention to electronic (eg, field effect transistors and logic circuits) and optoelectronic (eg, photodetectors, photovoltaics, and light emitting diodes) devices. Finally, the challenges and future prospects are considered based on the current advance of 2D TMDCs and related heterojunctions. This feature article reviews the state‐of‐the‐art research progresses that focus on the preparation and the applications in electronics and optoelectronics of two‐dimensional (2D) transition‐metal dichalcogenides (TMDCs) and their van der Waals heterojunctions. First, the preparation methods including chemical and physical vapor deposition growth are comprehensively outlined. Then, recent progress on the application of fabricated 2D TMDCs‐based materials is revealed with particular attention to electronic (eg, field effect transistors and logic circuits) and optoelectronic (eg, photodetectors, photovoltaics, and light emitting diodes) devices.