Eco-friendly Zn chalcogenide semiconductor nanocrystals (NCs)—including ZnS, ZnSe, ZnTe, and their alloys, which span zero-dimensional quantum dots, one-dimensional nanowires or nanorods, and two-dimensional nanoplatelets—are promising materials for advanced lighting and displays due to their heavy metal-free nature, excellent optical performance, and the wide bandgap tunability-enabled capability of light emitting from violet to red. Recently, significant progress has been made in Zn chalcogenide semiconductor NCs, encompassing the controlled synthesis of NCs and the applications in light emitting diodes (LEDs) and other optoelectronic applications. Herein, a systematic review of the controlled synthesis and device applications of eco-friendly Zn chalcogenide semiconductor NCs is provided for newcomers in this rapidly growing field, which helps steer its future development. First, this review introduces the nucleation and growth mechanisms of Zn chalcogenide semiconductor NCs, along with recent advancements. The focus is on growth models and the driving forces for NCs with different dimensions. Then, it discusses the controlled synthesis of NCs in terms of regulating shape, size, and surface chemistry, and the device structure design and charge transfer optimization for the application in LEDs, while also addressing the remaining challenges, such as optical performance and stability, along with promising solutions from the perspective of NCs and LEDs. Finally, other key optoelectronic applications such as photodetectors and photocatalysis are further discussed.