Branching (or tillering in grasses and related taxa) is an important trait of plant architecture and the result of axillary bud initiation and growth, which plays a crucial role in determining the seed yield of crops and forage yield. Multiple hormones and their interactions play key regulatory roles in the occurrence, growth and development of plant branching or tillering. In addition, environmental factors also regulate branching or tillering by changing the hormone contents and their balances within the plant. This study reviews multiple aspects of the mechanisms by which plant branching or tillering is regulated various hormones, including auxin, cytokinin, strigolactones, brassinosteroids, abscisic acid and gibberellins, ethylene, jasmonic acid, and complex regulatory networks formed by the interaction of different hormone signals. The aim is to establish a foundation for using hormone regulation mechanisms to cultivate new high-yielding crop plant growth forms with ideal plant architecture. The current issues with hormone regulation mechanisms controlling plant branching or tillering are also analyzed, and future research directions for hormone regulation mechanisms controlling plant branching or tillering are discussed, with the aim of providing a theoretical basis for using hormones to cultivate good varieties.