Fabricating a composite capable of detecting multiple analytes is important for advancing rapid medical diagnosis technology to assist in treating illnesses. A dendrimer-encapsulated Pt nanoparticle carbon nanotube (Pt-DEN-PANI-CNT) composite-based electrochemical biosensor was fabricated for the detection of hydrogen peroxide (H2O2), ascorbic acid (AA), and acetaminophen (AP), important for monitoring AP overdose-induced poisoning. Polyaniline (PANI) was used to coat single-walled carbon nanotubes (CNTs), which were then decorated with Pt-encapsulated, fourth-generation NH2-terminated poly(amidoamine) (G4-PAMAM) dendrimers. X-ray photoelectron (XPS) and attenuated total reflectance infrared (ATR-IR) spectroscopies, and transmission electron microscopy (TEM) were used to characterize the nanocomposite material. Electrocatalytic activity of the Pt-DEN-PANI-CNT composite was studied using cyclic voltammetry (CV) and chronoamperometric (CA) techniques. Point-of-zero charge (PZC) measurements showed that the isoelectric point of the composite was at pH 6.8, an important parameter to consider in explaining differences in selectivity of the composite to these various analytes. Measured chronoamperometric signals for AA, H2O2, and AP were found in the concentration ranges of 10 mu M-10 mM, 50 mu M-8 mM, and 20 mu M-1 mM, respectively. Within this series of analytes, the Pt-DEN-PANICNT composite can selectively detect both H2O2 and AP, separately, in the presence of the other analytes with rapid current response (<5 s) and good reproducibility.