A rapid assay for Cryptosporidium parvum (C. parvum) using piezoelectric-excited millimeter-sized cantilever (PEMC) sensor immobilized with goat polyclonal antibody was investigated for various concentrations from 10 to 1, 000 oocysts/ml. The resonant frequency of PEMC decreases when the target analyte attaches to the sensor. The high-modes of PEMC sensors exhibit mass change sensitivity in excess of a few femtograms. Using continuous flow experiments, we show that detection of 5oocysts/ml could be achieved in 15 minutes. Confirmation of detection was carried out using two strategies: (1) a low pH buffer caused antigen release causing resonant frequency increase, and (2) exposure to second binding antibody caused further mass increase and resonant frequency decrease. The results show that PEMC sensors can detect C. parvum oocysts at 5oocysts/ml. The PEMC-based detection method is also applicable to pathogens with the appropriate antibody immobilized on the sensor.