Amorphous indium gallium zinc oxide (a-IGZO) thin film transistor (TFT) biosensors were fabricated by surface modification of the a-IGZO TFT devices and the immobilization of Creatine Kinase (CK-MM) antibodies on the a-IGZO TFT devices. When the fabricated CK-MM a-IGZO TFT biosensors were used to detect CK-MM in the sample, both the field effect mobility and the Ion/Ioff ratio of the a-IGZO TFT devices were found to increase. These results indicate the potential applications for the developed a-IGZO TFT devices in biosensing.