This paper presents a sensitive and high cost-effective dual-parameter measurement technique, which is capable of measuring current and temperature based on Johnson noise thermometry (JNT) with the single tunneling magnetoresistive (TMR) sensor. The key is to utilize a TMR sensor with high sensitivity of 250 mV/V/mT to measure the current as well as temperature. Also, an ultra-low noise preamplifier with the equivalent noise as 3.1 nV/√Hz (@ 1 kHz) and a precise 10 μA constant current source are designed to implement the JNT and current measurement. Furthermore, a high-speed FPGA combined with ADC modules is used to carry out the signal processing algorithm and finally to calculate out the parameters of current and temperature. Finally, the dual-parameter sensing is verified by measuring current in the range of ±10 A and temperature ranging from -40 °C to 160 °C, respectively.