<p>Plant development and growth are impeded by numerous abiotic and biotic stresses, posing a serious threat to food security. Plants protect themselves from these threats by deploying various defence mechanisms. Jasmonic acid (JA) and salicylic acid (SA) are vital phytohormones that are key players in signalling pathways related to plant defence against biotic and abiotic stresses. JA is pivotal in defence against necrotrophic pathogens and herbivory, whereas SA is essential for resistance against biotrophic pathogens. They achieve this by regulating interactions with essential plant growth regulators (PGRs) such as abscisic acid (ABA), auxin, cytokinin, and ethylene (ET). This regulation maintains a balance between plant growth and defence against pathogen attacks by enhancing antioxidant enzyme activity, improving disease resistance, and promoting the accumulation of various compounds. This review explores the biosynthesis, signalling pathways, and molecular interactions of JA and SA, emphasising their crosstalk with other phytohormones such as auxins, ET, and ABA. The antagonistic and synergistic interactions between JA and SA in modulating plant immunity and stress responses are highlighted. Additionally, the regulation of JA and SA by various transcription factors in response to environmental vagaries, including drought, salinity, extreme temperatures, heavy metals, and UV radiation, is discussed. Advances in CRISPR (clustered regularly interspaced short palindromic repeats)-based genome editing for enhancing JA/SA-mediated stress tolerance and plant immunity are also reviewed to characterise SA/JA signalling dynamics across different plant species. Understanding the intricate regulation of JA and SA pathways offers promising strategies for developing climate-resilient crops with improved stress tolerance and productivity.</p>