Na3MnCO3PO4 has been predicted via ab initio calculations (Hautier et al., 2011) to have a high specific capacity of 191mAh/g, owing to its potential to deliver two-electron transfer reactions per formula via Mn2+/Mn3+ and Mn3+/Mn4+ redox reactions. This study demonstrates, for the first time, that Na3MnCO3PO4 can indeed display a specific capacity of 176.7mAh/g experimentally, reaching 92.5% of its theoretical. The low electronic conductivity is found to be the limiting factor for the previously observed low specific capacities for Na3MnCO3PO4. With a specific capacity as high as 176.7mAh/g, Na3MnCO3PO4 has a great potential to be a viable cathode material for Na-ion batteries.