The emergence of metal halide perovskite materials has triggered a revolutionary change in optoelectronic devices. Due to their outstanding optoelectronic properties and defect tolerance, metal halide perovskites can be used for a wide range of applications, including perovskite solar cells (PSCs), perovskite light-emitting diodes (PeLEDs), and perovskite photodetectors. However, the performance of perovskite-based optoelectronic devices is constrained by severe charge recombination at the interfaces between the perovskite film and charge transport layers. Self-assembled monolayers (SAMs) are attractive for addressing these interfacial issues. SAMs exhibit notable cost-effectiveness while providing superior optoelectronic characteristics, with potential for enhancement via tunable molecular engineering and optimization of ion–dipole interactions. Here, we review the recent advances of SAMs in perovskite-based optoelectronic applications by elucidating their role and function in different devices. Then we summarize the structure–function-performance relationships between SAMs and devices based on recent research. Finally, we provide a perspective on the role of SAMs in promoting practical applications by effectively improving the interfacial properties of perovskite-based optoelectronic devices.