Despite polyisothianaphthene's (PITN) desirable properties, complex synthetic routes and lack of solubility have limited its utility, particularly when thin films are required. Here, we report a one-step process for the simultaneous synthesis and film deposition of unsubstituted PITN using oxidative chemical vapor deposition (oCVD). The PITN film properties were easily tuned by controlling the substrate temperature over a range from 70 to 130 degrees C during the oCVD process. The positions of the absorption maxima in the UV-vis-NIR absorption spectra were considerably red-shifted by over 100 nm with increasing deposition temperature. This resulted in a decrease in the bandgap from 1.14 to 1.05 eV. Downshifts in many peak positions were observed in the Fourier transform infrared (FTIR) and Raman spectra with increasing deposition temperature. These observations suggest longer polymer conjugation lengths were achieved with increasing deposition temperature.