This work reports on the behavior of amino group-functionalized porous silicon (PS) intended to be used in bio-sensing and/or in medical applications. Amino-terminated organic layers were deposited onto silicon (Si) wafers and PS layers via 3-aminopropyltriethoxysilane (APTES) prepared in freshly hydrolysis solution. Fourier transform infrared (FTIR) spectroscopy was used to probe the absorption bands of NH2, CH2, SiO and SiHx groups forming in APTES-Si and APTES-PS complexes. The PS samples were dipped for different periods in hydrolyzed APTES solution. The increase in dipping time results in the disappearance of the Si-Si-H absorption bands, and the progressive apparition of the O-Si-H groups. After an adequate incubation time, all Si-Si-H and O-Si-H absorption bands disappear indicating a total functionalization of the PS layers