Phytohormones are key signalling molecules in developing responses in plants with various biotic and abiotic stresses. From the catalogue of well-known classical plant hormones, Jasmonic acid (JA) and its corresponding precursors and derivatives attract massive research attention by acting as potential methods for improving tolerance in diseased plants. Jasmonates are oxylipins chiefly derived from α-linolenic acids through the octadecanoid pathway. Plants synthesise this hormone in response to growth or defence-linked signs to coordinate plant development, growth or defence against numerous pathogenic microorganisms. Several reports emphasise the contribution of JAs in regulating vital physiological processes such as leaf senescence, tuber formation, photosynthesis, reproduction, seed germination and growth inhibition in plants. In response to pathogen exposure, JAs assume their operational task as a ‘master switch’, in charge of the initiation of signal transduction cascade, participating in the upregulation of genes associated with the production of alkaloids and phytoalexin, synthesis and accumulation of storage proteins, cell wall components and most importunately—stress ameliorative agents. This review focuses on recent findings connected to the structure, biosynthesis, regulation and signalling systems of JAs. In addition to this, the present article gives an essential insight into how the application of this phytohormone is involved in stress amelioration and induction of pathogenesis-resistant genes from an agriculturist, plant physiologist and biotechnologist’s point of view.