This work describes an approach for the selection and detection of specific DNA probes related to Toxoplasma gondii, a protozoan parasite responsible for toxoplasmosis. The detection system was developed on graphite carbon electrode modified with poly(3-hydroxybenzoic acid) sensitized with ToxG1 probe. The hybridization of the specific genomic DNA related to T. gondii showed good response by direct detection of guanine residue oxidation using differential pulse voltammetry (DPV). The biosensor was able to distinguish both the complementary and non-complementary targets and detect up to 100 ng μL−1 of the T. gondii genomic DNA. The hybridization (ToxG1: T. gondii genomic DNA) was confirmed by optical measurement. Optical assays using gold nanoparticles:ToxG1 probe showed a significant change in the absorbance peak in the presence of the T. gondii genomic DNA according to the electrochemical results. This novel biosensor shows potential as electrochemical transducer and was successfully applied in the biological sample.