<p>The increasing challenges, posed by plant biotic and abiotic stress, significantly impact agroecosystems, particularly in the context of rapid global climate change. Phytohormones function as critical chemical messengers, enabling plants to endure these stresses through a complex regulatory framework, thereby playing an essential role in plant survival. Recent research has increasingly underscored the significance of abscisic acid (ABA), in facilitating a prominent role under adverse conditions within plants. ABA has been shown to engage with major phytohormones, such as gibberellins (GAs), ethylene (ET), auxin, and cytokinins (CKs). It also interacts with several plant growth regulators (PGRs) and endogenous signaling compounds like brassinosteroids (BRs), strigolactones (SLs), nitric oxide (NO), salicylic acid (SA), melatonin (Mel), jasmonic acid (JA), polyamines (PAs), hydrogen sulfide (H₂S) and with secondary messengers like calcium ions. These interactions facilitate the equilibrium of resource allocation between plant growth and defense responses under suboptimal conditions. A thorough understanding of the intricate interrelationships among these phytohormones and PGRs under prevailing hostile environment, characterized by both synergistic and antagonistic actions, remains largely lacking. This exhaustive review elucidates the processes of ABA biosynthesis, metabolism, and its signal transduction pathways. Moreover, it sheds light on the complex crosstalk networks that exist among ABA, other phytohormones, PGRs and calcium in the face of various stress conditions, highlighting their pivotal roles in enhancing plant plasticity. The comprehensive insights presented in this review provide a molecular understanding of the phytohormonal pathways involved in improving environmental stress tolerance in plants and may serve as a foundational blueprint for developing precise strategies aimed at engineering climate-resilient crop cultivars.</p>