Na3PS4 has been demonstrated to be a promising solid electrolyte for all solid-state sodium ion batteries. Its high intrinsic ionic conductivity makes it ideal for high power battery applications. Although much research has been conducted on studying its structural and electrochemical properties, there is still no consensus on an optimal synthesis protocol despite a variety of reported Na3PS4 synthesis methods available. Here, we investigate the key parameters required to achieve single-step scalable synthesis of Na3PS4 solid electrolyte from its starting precursors. We determine that Na3PS4 solid electrolyte with high ionic conductivity (∼0.2 mS cm−1) can be easily achieved in 20 min using a single synthesis step, representing a significant improvement over other existing energy-intensive multiple-step methods. The all solid-state battery constructed with this highly conductive Na3PS4 is able to deliver 185 mAh g−1 capacity on the first discharge and excellent rate performance with a TiS2 cathode and a Na15Sn4 anode.