Alzheimer's Disease (AD) is the most common form of dementia associated with progressive loss of neuronal cells due to progressive accumulation of amyloid-beta (AB/Aβ) peptides in plaque form. Early diagnosis is the key to effective AD treatment, which can be carried out by detecting Aβ 1-40 (AB40) and Aβ 1-42 (AB42) potential biomarkers in easily accessible body fluids at sub pico gram per mL. With this aim, we have developed carboxylic functionalized multi-walled carbon nanotubes (fMWCNTs) embedded Polypyrrole (PPY) nanocomposite (PPY-fMWCNT) based highly sensitive and selective chemiresistive immunosensing platform that has the potential to detect multiple analytes simultaneously on the same substrate at sub femto gram per mL range. The binding event of antibody and antigen was transduced in terms of normalized resistance of bioelectrodes, measured through a four-probe probe station. By using PPY-fMWCNT as a bioelectrical transducer, the proposed sensing platform detected AB40 peptides (in real-time human plasma samples) in the linear detection range of 10 fg/mL to 10 ng/mL with a very low limit of detection (LoD) and a high sensitivity of 0.564 fg/mL and 55.67 ((ΔR/R0)/ng.mL-1)/cm2, respectively. The sensitivity of bare PPY (18.44 ((ΔR/R0)/ng.mL-1)/cm2) compared with fMWCNTs embedded PPY sensing platform enhanced 2.02 times without compromising in LoD. The analytical performance of the platform is further evaluated in terms of selectivity, repeatability and interference, posing its significance in the early detection of AD. © 2022 IEEE.