CsI(Tl)/PIN diode radiation sensors were fabricated for application in various fields such as an NDT and an environmental radiation monitoring system. CsI(Tl) crystals of 11×11×21mm 3 were processed as optical grade from a CsI(Tl) ingot and matched with PIN diodes in consideration of the light loss and the external impact. The photodiode signal is amplified by a low-noise preamplifier and a pulse shape amplifier. At room temperature, the fabricated CsI(Tl)/PIN diode radiation sensors demonstrate an energy resolution of 7.9% for 660keV gamma rays and 4.9% for 1330keV. The fluctuation of the directional dependency was below 14% from 0 to 90 degree for the incident 660keV gamma rays. The compactness, the low-voltage power supply and the physical hardness are very useful features for industrial applications of the fabricated CsI(Tl)/PIN diode sensor.