The synthesis of N-methyl-5-nitroindazolylacrylonitriles 2 a-l by a Knoevenagel condensation reaction with a series of aldehydes in the presence of piperidine allowed the preparation of the desired products the yields are good to excellent. N-Methyl-5-nitroindazolylacrylonitriles (2 a-l) were verified by 1 H, 13 C NMR and mass spectrometry. In this current work, the reactivity indices defined within the Conceptual DFT of the targeted molecules through DFT/B3LYP/6-311G(d,p) calculations were studied. The 1 H NMR, UV-vis and IR spectroscopy chemical shifts of all synthesized 5-nitroindazoles 2 a-l were calculated and the results were compared to the results of the experimental data. In this series of compounds, the 2 e has the lowest hyperpolarizability, which results being the most stable and having the least response to nonlinear optics (NLO). In contrast, the compound 2 l has the highest hyperpolarizability, which fallouts being the least stable and having a high response to NLO. Every chemical has a significant threedimensional p-electronic delocalization, which is crucial for understanding NLO responses.