This paper studies the liquid slug holdup of gas/non-Newtonian fluids in horizontal and inclined pipes. The results of the study show that the liquid slug holdup significantly increases for a given mixture velocity as the liquid phase becomes more shear-thinning. A new empirical correlation for estimating the liquid slug holdup is developed as a function of the Reynolds of liquid phase and inclination angle. The proposed equation is based on measured data consists of 271 data points with inclination angles ranging from 0℃ to 75℃ from horizontal. A good agreement is obtained between theory and experimental data. These results substantiate the general validity of the correlation presented for prediction of the liquid slug holdup in gas/non-Newtonian two-phase slug flow.