Dwell fatigue of titanium alloys used in aeroengine industry has threatened the reliability of aircraft for decades. Powder metallurgy (PM) through hot isostatic pressing (HIP) can fabricate titanium-alloy components with complex structures, and the mechanical properties are close to wrought alloys. Unfortunately, the dwell-fatigue behavior of the as-HIPed titanium-alloy powder components has not been reported in previous studies. The present work firstly investigated the effects of the peak stress (σp) and stress ratio (R) on the dwell-fatigue behavior and damage mechanism of the as-HIPed Ti-6Al-4V powder compact. With increasing σp, the dwell fatigue lives (NLCDF) decrease, but the dwell debit increases. The lowest NLCDF has been obtained at R = 0.1. With increasing R, the fatigue behavior of dwell fatigue is approaching to creep fatigue. When R is negative, the introduction of a lower reverse stress reduces the cumulated max plastic strain, resulting in the increment of NLCDF. Moreover, a crack-initiation and propagation model based on soft-hard grain pairs has been proposed to describe the dwell-fatigue mechanism. In addition, the dwell debit of PM Ti-6Al-4V alloys is similar to or even lower than that of wrought alloys. Improving the microstructure homogeneity of the material may be the key to further reducing the dwell effect.