Earth dams' failure may occur due to different reasons such as structural instability conditions, hydraulic conditions, seepage through the dam body and/or rapid drawdown. The determination of factor of safety for the dam slope stability, under different cases of operations, is vital to ascertain the dam overall safety. In this work, Finite Element modeling is employed for simulating seepage and stress analysis of earth dam problems via GeoStudio software. Thus, phreatic seepage surface, pore water pressure distribution and total hydraulic head variation of an earth dam are analyzed. The model is verified, then it is employed to analyze seepage and stability of Mandali Dam (Iraq). Three different cases of operation are considered; end of construction before filling the reservoir, steady state seepage and rapid drawdown of the reservoir. Four major analytical methods are used to assess the stability of the dam side slopes; Ordinary Method of Slices, Bishop, Janbu and Morgenstern and Price. Benchmark safety regulation criteria (USACE and BDS) are obeyed. The results of the analysis presented in this paper confirm the safety of Mandali dam against combined seepage and slope stability under all cases of operation. The case of rapid drawdown is the most critical operating case; compared to other cases of operation.