All-solid-state sodium batteries with sulfide-based solid electrolytes are attracting attention as next-generation energy storage systems to replace Li-ion batteries, owing to their improved safety and the abundant sodium resources. Na3PS4-based materials, which have relatively high conductivities and favorable mechanical properties, make promising Na-ion solid electrolytes for realizing all-solid-state sodium batteries. However, it is essential to establish a further simple and effective protocol for manufacturing such solid electrolytes and composite electrodes. In this study, Na3-x PS4-x Cl x (x = 0, 0.0625) was prepared by a liquid-phase (suspension) process from Na2S, P2S5, and NaCl using 1,2-dimethoxyethane as a reaction media. Na3PS4 heated at 400 °C and Na2.9375PS3.9375Cl0.0625 heated at 480 °C exhibited Na-ion conductivities of 2.6 × 10−4 and 4.3 × 10−4 S cm−1 at 25 °C, respectively. A homogenous composite electrode was prepared with TiS2 active material and Na3PS4 solid electrolyte via the simple liquid-phase process, resulting in large contact areas between electrode and electrolyte particles. The electrode obtained by liquid-phase provided an all-solid-state cell with higher reversible capacity of 161 mAh g−1 than a conventional mechanically mixed electrode. Suspension syntheses of Na3-x PS4-x Cl x are useful for the simple production of solid electrolytes and are highly applicable to all-solid-state sodium batteries.