The Streptococcus pneumoniae detection plays an important role in the diagnosis and monitoring of pneumococcal diseases. A genosensor based on graphite electrodes modified with polymer was developed for such detection. First, the poly(4-aminophenol) film was electrochemically deposited on a graphite electrode. Afterward, an S. pneumoniae-specific oligonucleotide (Strep1), isolated from conserved regions of the bacterial genome, was immobilized onto the modified electrode surface and used for the test with complementary target oligonucleotide (Strep2) or genomic DNA. The genosensor was evaluated using electrochemical techniques and atomic force microscopy. Poly(4-aminophenol) film caused an increase in probe immobilization, monitoring the guanine oxidation peak. The detection limits obtained using differential pulse voltammetry and electrochemical spectroscopy impedance were 54 and 28ngmL(-1), respectively. The novel genosensor was efficient for the immobilization and detection of S. pneumoniae genomic DNA. POLYM. ENG. SCI., 58:1308-1314, 2018. (c) 2017 Society of Plastics Engineers