We propose a twisted microfiber interferometer sensor coated with boron nitride (BN) nanosheets for simultaneous measurement of relative humidity (RH) and temperature ($ T $). Sensitive material characteristics (BN nanosheets) enhance refractive index (RI) sensing sensitivity of proposed devices. A twisting process on the microfiber surely improves the evanescent field interaction with the deposited layer. The experimental results show that the RH sensitivities are ${-}{121.6}\;{\rm pm}/\% {\rm RH}$ and 0.26 dBm/%RH for humidity range from 46% to 72% and $ T $ sensitivities of 23.5 pm/°C and ${-}{0.045}\;{\rm dBm}/^\circ {\rm C}$ from 50°C to 90°C. The twisted microfiber interferometer has the advantages of compact structure, high sensitivity, and multiparameter measurement, which has certain potential for more applications.