A novel temperature-insensitive strain sensor, based on an in-line Mach-Zehnder interferometer, is fabricated by concatenating two waist-enlarged fiber tapers separated by a short piece of photonic crystal fiber. The interference spectrum of the proposed sensor is analyzed in detail. Experimental results demonstrate that this sensor has a strain sensitivity of 3.02 pm/\mu \varepsilon and maintains the temperature insensitivity feature. The proposed sensor has great potential in diverse sensing applications due to its advantages, such as its compact size, low cost, and simple fabrication process.