Determination of internal stability of reinforced soil walls under earthquake conditions is an important part of seismic design. The horizontal method of slices is used for determining internal stability or tieback analysis of the reinforced soil wall. A pseudo-dynamic method is adopted in the present analysis, which considers the effect of phase difference in both the shear and primary waves traveling through the backfill due to seismic excitation. Reinforced soil walls with cohesionless backfill material have been considered in the analysis. Results are presented in graphical and tabular form to show the required tensile force and length of geosynthetic reinforcement to maintain the stability of the reinforced soil wall under seismic conditions. Effects of variation of parameters such as soil friction angle, and horizontal and vertical seismic accelerations on the stability of the reinforced soil wall have been studied. With increase of seismic accelerations both in horizontal and vertical directions, stability of the reinforced soil wall decreases significantly and thus needs greater strength and length of geosynthetic reinforcement to maintain stability of the wall. The seismic vertical acceleration in an upward direction gives higher values of required geosynthetic tensile strength, and the seismic vertical acceleration in the downward direction yields higher values of length of geosynthetic reinforcement. Comparisons of present results with available pseudo-static results are shown and the limitations of the pseudo-static results are highlighted.