This work proposes the use of the composite carbon felt/carbon nanotube/Polyaniline as an alternative for applications as a pH sensor device. The carbon felt/carbon nanotube is an electronic conductivity material that was obtained from polymer felt (poliacrilonitrile felt) using oxidation and carbonization processes. The cup-stacked and bamboo-like tubes were grown on the fibers of carbon felt by chemical vapor decomposition method. The sensor was obtained by incorporating polyaniline (Pani) on the nanotubes present on the fibers of carbon felt/carbon nanotubes composite. The measuring process uses an EGFET (Extended Gate Field Effect Transistors) configuration, which is a derivation of the ISFET (Ion Sensitive Field Effect Transistor) - that is basically a chemical semiconductor sensor. The drain-current versus source-drain voltage is presented for varying pH concentrations from 2 up to 12.