The purpose of this research is to ev aluate the effectiveness and financial feasibility of the old age pension (Notional Defined Contribution) schem e in Mongo lia in the context of its changing demographic dynam ics by developing an Excel-based dynam ic model. We find that the current scheme will experience consider able financial deficit due to its d esign flaws. The simulation r esults f rom two policy scenar ios – increased national pension age and increased contributions rates – suggest that the financial deficit of the scheme will become worse. Given the results, a Funded Defined Contribution schem e is examined to establish an ef fective and sustainable pension system in Mongolia