Compared to polymer‐based organic solar cells, all‐small‐molecule organic solar cells (ASM‐OSCs) have garnered significant attention due to their well‐defined chemical structures, lower batch‐to‐batch variation, straightforward synthesis and purification procedures, and easy to modulate properties. Recent developments in small molecule donors have enabled ASM‐OSCs to achieve power conversion efficiencies in excess of 17%, gradually approaching those of polymer‐based devices, and demonstrating considerable potential for commercialization. However, structural and morphological features in the all‐small‐molecule blend films, including crystallization behavior, phase separation, and molecular arrangement, play a crucial role in the photoelectric performance. This review systematically introduces and discusses recent advancements in ASM‐OSCs in terms of design strategies for novel small molecule donors and device engineering. Additionally, the correlation between active layer morphology and structure and device performance is analyzed. Finally, the challenges and prospects of ASM‐OSCs are discussed.