Recently, the pyridazine nucleus has been widely studied in the field of particular and new medicinal factors as drugs acting on the cardiovascular system. Additionally, a number of thienopyridazines have been claimed to possess interacting biological macromolecules and pharmacological activities such as NAD(P)H oxidase inhibitor, anticancer, and identified as a novel allosteric modulator of the adenosine A1 receptor. The literature survey demonstrates that coumarin, 1,2-pyrazole benzothiazole, and 1,3- thiazole scaffolds are the most versatile class of molecules. In this study, a series of substituted pyrazole[3,4-d]pyridazine derivatives (2a-n) were prepared, and their structures were characterized by Mass analysis, NMR, and FT-IR. These obtained pyrazole [3,4-d]pyridazine compounds were very good inhibitors of the carbonic anhydrase (hCA I and II) isoenzymes and acetylcholinesterase (AChE) with K-i values in the range of 9.03 +/- 3.81-55.42 +/- 14.77 nM for hCA I, 18.04 +/- 4.55-66.24 +/- 19.21 nM for hCA II, and 394.77 +/- 68.13-952.93 +/- 182.72 nM for AChE, respectively. The possible inhibition mechanism of the best-posed pyrazole[3,4-d]pyridazine and pyrazole-3-carboxylic acid derivatives and their interaction with catalytic active pocket residues were determined based on the calculations.