In this paper, a dual Mach-Zehnder interferometer for measuring both temperature and strain is proposed and verified by experiments. The sensor configuration involves cascading a four-core fiber and a double-clad fiber between two single-mode fibers. By exploiting the different responses of the two Mach-Zehnder interferometers to temperature and strain, we construct a matrix using two selected resonance dips from the transmission spectra, so that both temperature and strain can be measured simultaneously. The experimental results show the sensor’s remarkable performance, with the maximum temperature sensitivity of −94.2 pm/℃ and the maximum strain sensitivity of 2.68 pm/με. The maximum temperature error and strain error are found to be ±0.35 ℃ and ±4.8 με, respectively. Compared with other optical fiber sensors, the sensor has high sensitivity, a simple structure, and ease to manufacture and implement, making it a structure choice for applications in quality inspection of materials.