A photochromic spironaphthoxazine group has been covalently bonded in the 3 position of thiophene (I) and in the 3’ position of terthiophene (II). The electrochemical and spectroscopic properties of these compounds have been characterized, together with their photochromic properties, associated with the ring opening of the naphthoxazine moiety under light excitation, which occurs in solution and even in the solid state of these compounds. Electropolymerization into spironaphthoxazine functionalized poly(thiophenes) is only successful with II, due to the relief of steric hindrance and electronic effects on the thiophene units in this compound. The much lower photochromic properties of poly(II) are associated with the compactness of this polymer.