The physisorption property of toxic acrylonitrile (AN) molecule on armchair arsenene nanoribbon (Arm-AsNR) was explored with density functional theory (DFT) method. The structural solidity of pristine Arm-AsNR is confirmed in terms of formation energy, and dynamic stability is authenticated based on phonon-bands. The main focus of this research study is to investigate AN using Arm-AsNR. The physisorption of various preferential adsorption sites (V, T, R, B, and parallel sites) of AN molecules are studied in connection with the Bader charge transfer, energy gap, and adsorption energy. Favorably, the negative value of adsorption energy is noticed upon the physisorption of AN on Arm-AsNR, and it is in the range of -0.583 to -1.009 eV. The novel outcomes of the proposed research work recommend that the Arm-AsNR can be efficiently used as a base substrate to detect the presence of AN molecules.