Fiber containing power law fluids are widely used as drilling/fracturing fluids to improve wellbore cleaning efficiency or enhance proppant transport in the oil and gas industry. Understanding the settling behavior of solids in fibrous fluids is critical for designing and optimizing fiber containing fluids. In this paper, an new equation for predicting the settling velocity of solids in fiber containing power-law fluids is presented. Settling tests recorded by a high-speed camera were conducted, considering fiber concentration, sphere diameter, particle density and base fluid rheology. The microscopic observation shows that numerous filaments disperse in the base fluid, inter cross together, and form the fiber network. The fiber network causes a minor change in the base fluid rheology, and reduces sphere settling velocity by exerting the mechanical drag, called fiber drag force to the settling sphere. To quantify the fiber drag force, a revised definition of the fiber drag coefficient is made and proved to be fit for spheres with different densities. The sum of fiber drag coefficient and viscous drag coefficient is called as total drag coefficient. A non-dimensional term that is the function of total drag coefficient is defined that is independent of the sphere settling velocity. Finally, the settling velocity equation is obtained by correlating the non dimensional term versus the particle Reynolds number (0.002-416), fiber concentration(0.02%-0.10% by weight) and flow behavior index. The predicted settling velocity is in good agreement with the measurement, with an average relative difference of 12.49%. The key findings of this work are expected to provide a basis for better the application of fiber containing power-law fluids. (C) 2018 Elsevier B.V. All rights reserved.