The thermo sensors were fabricated using the indigenously developed lead free thick film NTC thermistor pastes. The prepared thermo sensor device showed the resistance of the films decreases exponentially with respect to increase in temperature, very good sensitivity index/thermistor constant (ˇ = 4045 K), repeatability and reproducibility and responsivity (28.79/mW) to IR. Therefore, the developed lead free thermo sensor can be effectively used as Infra-red detector.