In this paper, we present a secure circuit with a low-power on-chip temperature sensor for the detection of temperature fault injection attacks. Such attacks stress an electronic circuit by heating it beyond the allowed operation temperature range, inducing random modifications of the data in the memory cell or limiting the function of the target device. The objective of the proposed secure circuit with an on-chip temperature sensor is to detect temperature-based fault injection attacks and protect the secure contents of the target device. The proposed secure circuit detects and allows the shutdown of the protected circuit when the temperature is below −10 ℃ or above 80 ℃. The protected circuit operates normally in the operation temperature range from −10 to 80 ℃ and can be shut down by the control block of the secure circuit outside of this operation temperature range. The proposed secure circuit has a simple structure and a small active area, and consists of a low-power temperature sensor, two comparators, and an XOR gate. It is fabricated using a standard 0.18 μm complementary metal-oxide-semiconductor (CMOS) process with a small active area of 0.04 mm2 and consuming 19.72 μW with a 1.8 V power supply.