A series of heterocyclic compounds incorporating pyridazine moiety were for diverse biological activities. Pyridazines and pyridazinones derivatives showed wide spectrum of biological activities such as vasodialator, cardiotonic, anticonvulsant, antihypertensive, antimicrobial, anti-inflammatory, analgesic, anti-feedant, herbicidal, and various other biological, agrochemical and industrial chemical activities. The results illustrated that the synthesized pyridazine/pyridazine compounds have diverse and significant biological activities. Mechanistic insights into the biological properties of pyridazinone derivatives and various synthetic techniques used for their synthesis are also described.