A new fiber catalyst for Knoevenagel condensation has been prepared by aminating a commercially available polyacrylonitrile fiber with N,N-dimethyl-1,3-propanediamine. The fiber catalyst was characterized by elemental analysis, X-ray powder diffraction spectra (XRD), scanning electron microscopy (SEM) and Fourier-transfer infrared spectroscopy (FTIR). The Knoevenagel condensation proceeded smoothly in the presence of the fiber catalyst and the products were obtained in excellent yields. This catalyst is applicable to a wide range of aromatic aldehydes. Moreover, the reaction can be easily carried out in different solvents of varying polarities. The newly developed fiber catalyst was also found to exhibit excellent recyclability and reusability (up to 10 times) without any additional treatment.