Seed plants have evolved to maintain the dormancy of freshly matured seeds until the appropriate time for germination. Seed dormancy and germination are distinct physiological processes, and the transition from dormancy to germination is not only a critical developmental step in the life cycle of plants but also important for agricultural production. These processes are precisely regulated by diverse endogenous hormones and environmental cues. Although ABA (abscisic acid) and GAs (gibberellins) are the primary phytohormones that antagonistically regulate seed dormancy, recent findings demonstrate that another phytohormone, auxin is also required to induce and maintain seed dormancy and therefore might act as a key protector of seed dormancy. In this review, we summarize current understanding of the sophisticated molecular networks involving the critical roles of phytohormones in regulating seed dormancy and germination, in which AP2-domain-containing transcription factors play the key roles. We also discuss the interactions (crosstalk) of diverse hormone signals in seed dormancy and germination, focusing on the ABA/GA balance that constitutes the central node.