In this study, we introduced an integrated biosensor system that can achieve fish stress monitoring (real-time detection of glucose level as stress indicator) and visualization (a color of green, yellow, or red according to the stress level), realized using a multifunctional LED. The glucose concentration measurement by this system is based on the principle of converting the output current value obtained from the biosensor into a voltage value on an electronic substrate circuit. The stress visualization is based on the principle of switching the lighting color of the LED by setting the switching reference value (Vcomp) on the electronic substrate circuit and comparing Vcomp and the output voltage value (Vout) of the biosensor. First, glucose standard solution was used to calibrate the electronic substrate circuit by calibrating Vcomp according to changes in Vout. Next, the sensor was attached to the test fish (Oreochromis niloticus) to evaluate the practical use of the system. Then, the concentration of dissolved ammonia in water was changed to 10 and 20 mg L−1 as a stress factor, and the stress response and LED lighting color switch according to the stress response were examined.