In this work, electrospun polyaniline (PANI) micro/nano dots on quartz crystal microbalance (QCM) sensor were used to sense the humidity at room temperature. A QCM humidity sensor is made by coating a low-cost commercial quartz crystal resonator with Polyaniline (PANI), which is one of the most promising polymers for sensing applications due to its relatively high stability. The electrospinning technique is used to coat the PANI nanometer-scale thin film to the electrode of quartz crystal. From experimental results, it was found that PANI coating on the QCM electrode is an effective way to improve humidity-sensing characteristic of QCM sensor. The PANI coated sensor has good response to the humidity with short response and recovery times. The experimental results show that the humidity sensitivity of PANI coated QCM sensor considerably depends on the thickness of PANI layer coated on the sensor electrode.