The current work intends to unveil the performance of thermal treatment in improving the biodegradability of waste activated sludge (WAS). The thermal treatments of WAS were conducted at different temperatures (30oC, 60oC, 75oC, 90oC) as well as treatment durations (0, 1, 2, 4, 8, 16 hours), and its effects on the sludge biodegradability were measured in terms of soluble chemical oxygen demand (SCOD). The ANOVA analysis showed that both treatment temperature (P<0.001) and duration (P<0.001) had significantly enhanced the biodegradability of WAS. Accordingly, the results showed that the SCOD increased with increasing treatment temperature, with 90oC thermal treatment at 16 hours producing the highest SCOD of 163.39g/L. Although SCOD increased with longer treatment duration, the highest SCOD increment happened within the first 4 hours of treatment before slowing down gradually. Besides, the interaction between treatment temperature and duration was also significant (P<0.001). This was because the effect of treatment duration becoming less significant when the treatment temperature was raised. Finally, the energy-effective thermal treatment condition was found to lie between 75oC and 90oC within 2 to 4 hours in achieving the highest concentration of SCOD per consumed energy of 0.27 -0.32 g/L per kJ. Hereafter, the impending study is to administer the treated WAS for growing black soldier fly larvae, targeting to produce valuable larval biomass feedstock for biodiesel industry. © 2023 Author(s).