Synthesis, characterization and application of the polyaniline-diatomite (PAD) composite in the adsorption of Reactive Red 120 (RR 120) and Acid Blue (AB) dyes were carried out. The composite was prepared by the in situ polymerization of aniline. Mass of purified diatomite was mixed with a solution containing aniline dissolved in 2M hydrochloric acid at room temperature. The solid obtained was characterized using the SEM, XRD and FTIR analyses. The kinetic adsorption of dyes was described using the pseudo-second order kinetic model. The adsorption isotherm of the RR 120 dye can be fitted by the Freundlich adsorption isotherm model. However, the adsorption isotherm of the AB dye can be better fitted by the BET model.