Abstract: Delay of germination 1 (DOG1) is a master regulator of seed dormancy and cooperates with abscisic acid (ABA) to delay seed germination. The core ABA signaling pathway and DOG1 pathway converge in protein phosphatase 2C (PP2C). DOG1 requires PP2C to regulate seed dormancy and enhances ABA signaling by binding to ABA HYPERSENSITIVE GERMINATION 1/3 (AHG1/AHG3). DOG1 suppresses AHG1 activity to increase ABA sensitivity and induce seed dormancy. In recent years, significant progress has been made in research on the regulation of seed dormancy and germination by DOG1. In this review, we summarize research achievements in this field, including the role of DOG1 in seed maturation, dormancy, and germination, the transcriptional regulatory mechanisms of DOG1 expression, and the regulation and action mechanism of DOG1 on seed dormancy and germination. We also highlight scientific issues that need to be further investigated in this field.