Lensless imaging allows for designing imaging systems that are free from the constraints of traditional imaging architectures. As a broadly investigated technique, mask-modulated lensless imaging encodes light signals via a mask plate integrated with the image sensor, which is more compacted, with scalability and compressive imaging abilities. Here, we review the latest advancements in mask-modulated lensless imaging, lensless image reconstruction algorithms, related techniques, and future directions and applications.