To develop an efficient simultaneous drying and disinfesting treatment for in-shell walnuts, a 2.4 kW, 27.12 MHz 50 Ω radio frequency (RF) system and a two-stage strategy were applied to investigate the effects of electrode gap, heating rate, and transition temperature on drying characteristics, disinfesting efficacy, and product quality. Peroxide value (PV) and free fatty acid (FFA) of walnuts with different packages during accelerated storage were also evaluated. The electrode gap of 160 mm for one-stage drying was selected for further investigations since it can ensure a short processing time (210 min), 100% mortality of C. cephalonica larvae, and eligible PV (0.183 meq/kg) and FFA (0.128%). The two-stage strategy with the heating rate of 5 °C/min and transition temperature of 55 °C shortened the drying duration to 170 min by nearly 20%, improved the heating uniformity index from 0.075 to 0.064, and reduced crack ratio from 43.75 to 26.04% significantly (P < 0.05) as compared to one-stage treatment. PV and FFA of vacuum and normally packaged walnuts still met the industrial standard after the 20-d accelerated storage. Therefore, the developed two-stage simultaneous RF treatment is recommended for further industrial applications owing to the shortened processing time and improved product quality.