A Mach–Zehnder interferometer based on S-taper embedded in long-period grating (LPG) for simultaneous measurement of strain and temperature is proposed. The LPG is written using CO₂ laser in a single-mode fiber. Then an S-taper is made by putting the LPG in a fusion splicer and applying off-axis pull at the middle point. The spectral characteristics of strain and temperature are investigated theoretically and experimentally. The experimental results show that the maximum strain sensitivity is 53.6  pm  /  με within a strain range of 0 to 373.13  με. In additionally, the proposed sensor has a maximum temperature sensitivity of 70  pm  /    °  C when the temperature varies from 30°C to 90°C. Further analysis shows that this sensor could be applied for simultaneous measurement of strain and temperature.