An optical fiber Fabry–Perot (F–P) humidity sensor was fabricated using polyvinyl alcohol (PVA) and a single-mode optical fiber. Humidity response experiments were carried out in the humidity range of 22–98% RH with a cycle of rising and falling humidity to investigate the repeatability of its response to humidity. The sensitivity was 36.71 pm/% relative humidity (RH) with linearity of 0.99773 under rising humidity and 37.63 pm/% RH with linearity of 0.99846 under falling humidity. The experimental results showed that the humidity sensor has good repeatability and consistency. Typical tests under 75% RH were performed to obtain the dynamic response characteristics. The dynamic response wavelength drift was measured repeatedly, which showed a high response speed. The response time and recovery time were 1.5 and 2.5 s, respectively. Furthermore, the dependence of the response characteristics on the cavity length and PVA concentration was investigated. The experimental results showed that the sensor maintains a highly linear response to humidity over a wide range of RH regardless of the cavity length and PVA concentration. The research results indicate the possibility of realizing an easily fabricated, low-cost, and high-performance optical fiber humidity sensor.