The progress in the development of a piezoelectric immunosensor for the detection of a secretion protein (38 kDa) from Mycobacterium tuberculosis are described. A high affinity and specificity monoclonal antibody was obtained from a recombinant form of the target protein. This immunoreagent was employed for the development of a competitive ELISA, as a previous diagnostic test and reference assay for the characterization of the future biosensor. The ELISA detection limit was 14 ng/mL of the 38kDa antigen. The first experimental approach to the piezoelectric immunosensor was undertaken using bovine serum albumin (BSA) as a model antigen and 10 MH piezoelectric crystals as the biosensor transducer element. The obtained results show that high frequency crystals (≥ 100 MHz) should be used in order to reach the high sensitivity required for diagnostic purposes. These crystals would allow obtaining high and stable assay signals using very low protein concentrations for crystal functionalization, thus enhancing immunosensor sensitivity. Preliminary experiments have proved the successful and efficient immobilization of the 38 kDa antigen on high fundamental frequency (HFF) crystals (100 MHz). Moreover, the functionalized surface seems to be able to selectively bind the monoclonal antibody specific to the target antigen.