Capacity expansion of the existing Municipal Solid Waste (MSW) landfill is accompanied using an engineering berm, which is a better alternative to new landfill construction. In the present study, the pseudo-static seismic stability analysis of a side-hill type expanded landfill using a limit equilibrium approach considering a pre-determined failure surface along the liner was performed. The heterogeneity of the waste mass was incorporated by considering the change in waste unit weight with depth. Over-berm failure condition (when the waste mass slides over the back slope of the berm) was considered for a landfill. Close-form solutions for the average factor of safety (FSavg) were developed. Different parametric variations were performed for the landfill and it was found that the average factor of safety (FSavg) increases with an increase in the internal friction angle of the waste mass for different berm heights. It was also found that the FSavg increases with an increase in the height of the berm and also increase with an increase in the back slope of a berm.