Plant hormones and environmental factors play central roles in the regulation of growth, development, nutrient allocation, and source/sink transitions. Plant hormones play important functions in regulating developmental processes and signaling networks involved in plant responses to a wide range of biotic and abiotic stresses. The response and adaptation of plants are determined by complex interactions with metabolites, plant growth regulators (PGRs), secondary messengers, and downstream defense and/or homeostasis genes. Plants produce a wide variety of hormones that include abscisic acid (ABA), auxins, brassinosteroids, cytokinins, ethylene, gibberellins, jasmonic acid (JA), methyl jasmonate (MeJA), and salicylic acid (SA). Apart from the PGRs, vital environmental cues, such as light and temperature, also entrain several physiological processes in plants. Hence, in this chapter, the various roles of environmental factors and plant hormones in the regulation of plant growth and development are discussed.70