I2C (Inter-Integrated Circuit) interface is one of serial communication which often used on electronic device, sensor and microcontrooler more than UART and ISP. This communication is very flexible because it can used by 128 devices in 1 bus with high transfer-rate. When design a product which has many devices on it, this communication is better than others. But, not all electronic devices has I2C communication. Therefore, the goals in this research is to make an I2C interface addition device for sensor which doesn’t have it. The sensor used is the MH-Z19 CO2 sensor which able to measure the level of carbondioxide in the air. MH-Z19 just has UART as the serial communication and PWM. The result of this research is an I2C interface device on CO2 sensor MH-Z19. The design of I2C interface is based on the microcontroller minimum system. The dimensions of this interface in accordance with the dimensions of the MH-Z19 sensor and using the SMD components. This interface used arduino as the programming system and the data of carbondioxide measurement from MH-Z19 is sent by I2C interface towards other devices through I2C communication. In the test, I2C interface sent the data of sensor to arduino and raspberry pi. All the data that had been sent accepted by arduino and raspberry with the percentage of error data is 0,028%.