Electrochemical analysis of cobalt(III) protoporphyrin IX (CoP), synthesis and characterization of CoP nanoparticles, and signal amplification for biosensor development is presented. CoP was self‐assembled into nanoparticles and then released to produce over 1000 electrochemically‐detectable molecules for each protein target of interest, in this case monoclonal rabbit antibody. Anodic stripping voltammetry was utilized for quantitative and sensitive detection of CoP which correlated to target protein concentration. The CoP limit of detection was 4 nM and target protein was detected at 100 pM. This combination of nanoparticle and electrochemical signal amplification could allow for sensitive, inexpensive, and portable detection of protein biomarkers.