The evaluation of seismic active earth pressure acting on narrow backfilled retaining walls is more essential during earthquake loading to ascertain safety and economical design. This paper proposes an analytical procedure to evaluate seismic active earth pressure for narrow backfill width retaining walls using the limit equilibrium method under earthquake loading. The existence of rock behind the retaining wall that affects the size and shape of the failure wedge in narrow backfill soil is considered. The study also accounts for the strain softening behavior under earthquake loading by considering the change in shear strength due to the reduction in friction angle from peak to residual along the bilinear failure slip surfaces in backfill soil. The formation of multiple failure surfaces due to multiple failure wedges in the narrow backfill soil is also considered. The proposed values of seismic active earth pressure are validated by comparing the obtained results with the earlier studies. The influence of backfill soil friction angle, dilatancy angle, interface friction angle between the retaining wall and backfill soil, interface friction angle between the rock face and backfill soil, backfill slope angle, rock-face slope angle, and the distance of constraint rock face boundary from retaining wall on the magnitude of seismic active earth pressure and its point of application are presented. © 2021, Indian Geotechnical Society.