Polymer composites containing alginate (AL) and treated multiwalled carbon nanotubes (TMWNT) were prepared by dispersing different weight percentages of TMWNT. The resulting composites were characterized by Fourier transform infrared spectroscopy (FTIR) and UV-vis spectroscopy (UV). The morphology of the composites was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the thermal stability and crystallinity embedded in the composites were analyzed by thermogravimetric analysis (TGA) and X-ray diffraction (XRD). The results of the characterization, morphology, thermal stability as well as diffraction studies clearly show that the alginate-TMWNT (AL-NT) composites are formed by dispersing the TMWNT into the AL polymer matrix. In addition, the AC electrical conductivity of the composites was also studied in the frequency range, 350 KHz-2.3 MHz. The frequency and temperature dependent AC conductivity of the AL-NT composites was strongly affected by the dispersed concentration of TMWNT.