This Project describes a design of an effective temperature monitoring system by using GSM technology of wireless communication. A GSM modem provides the communication interface. It transports device protocols transparently over the network through a serial interface. A GSM modem is a wireless modem that works with a GSM wireless network. This GSM Modem can accept any GSM network operator SIM card and act just like a mobile phone with its own unique phone number. Advantage of using this modem will be that you can use its RS232 port to communicate and develop embedded applications. Applications like SMS Control, data transfer, remote control and logging can be developed easily. The modem can either be connected to PC serial port directly or to any microcontroller. This project will be used in industries or homes or where we want to monitor the temperature using GSM technology. This project is designed in such a way that A GSM modem is interfaced to the controller using serial communication. The temperature sensor will be interfaced to the controller through an ADC to convert the analog value sensed into the digital value .The microcontroller continuously monitors the status of the sensor. Whenever the user wants to know the temperature value he has to send a predefined message to the modem. The modem receives the predefined message and intimates the same to the microcontroller. Now, it is the job of the microcontroller to read the value from the corresponding sensor process it and send the requested value to the user mobile. The controller will also be programmed in such a way that it alerts the buzzer, if the sensed temperature crosses the pre set value. A buzzer interfaces to the controller gives an audio indication of over temperature. A 16X2 LCD will be interfaced to the controller to display the value of the temperature. This project uses regulated 5V, 500mA power supply. 7805 three terminal voltage regulator is used for voltage regulation. Full wave bridge rectifier is used to rectify the ac output of secondary of 230/12V step down transformer.