Electrocaloric cooling systems require components with large entropy change at the desired working temperature, high electric breakdown strength and low dielectric losses. We here report on hydrothermal synthesis (HTS) route for preparation of lead-free electrocaloric (EC) material Ba_0.82Sr_0.18Sn_0.065Ti_0.935O₃ (BSSnT-18-6.5) with a median particle size of d₅₀ = 150 nm. Influence of molar ratio (Ba,Sr):(Sn,Ti) on the purity and particle size of hydrothermally synthesized powders is investigated. The sintering behavior and the resulting microstructure of bulk ceramic samples prepared with HTS powders as well as their dielectric, ferroelectric, and electrocaloric properties are analyzed and discussed in detail. By using HTS powders we could significantly reduce sintering temperature from 1400 °C to 1275 °C. Samples prepared with a molar ratio (Ba,Sr):(Sn,Ti) of 1.6 show a maximum EC temperature change |ΔT_EC| of 0.59 K around 30 °C with a broad peak of |ΔT_EC| > 0.3 K in the temperature range from 5 °C to 65 °C under an applied electric field change of 5 V μm⁻¹. Our results show that hydrothermal synthesis is well suited to produce starting powders of lead-free electrocaloric materials for future fabrication of multilayer ceramic (MLC) components.