Reduced atmosphere firing of (Na0.5K0.5)NbO3 (NKN) ceramics opens up an important opportunity for lead-free piezoelectric materials; one of the promising applications is base metal cofired multilayer actuators. Here, we extend an investigation on the effects of reduced atmosphere firing (PO2 = 10−10 atm) on the piezoelectric properties and associated point defects in NKN–LiF ceramics. To access the domain dynamics contribution to the converse piezoelectric properties and consider point defects in the sintered ceramics, Rayleigh analysis and thermal stimulated depolarization current (TSDC) were used. The piezoelectric properties and Rayleigh analysis of NKN–LiF ceramics demonstrated that the intrinsic and extrinsic piezoelectric response is essentially independent of firing atmosphere. Furthermore, reduced fired ceramic was found to have much higher resistivity than in the air-fired case. From the TSDC analysis, the space charge in the reduced fired ceramic was considered to be much smaller than in the air-fired ceramic, implying that the alkali volatilization was suppressed in reduced fired NKN–LiF ceramic.