In this study, the effects of triiodothyronine (T3) were evaluated on the NLRP3 inflammasome complex formation in the hippocampus of the rat with restraint stress-induced depressive-like behaviors.Thirty-six Wistar male rats were randomly allocated to the following groups: Control, Model, and Model + T3. In Model or Model + T3 group, a single dose of PBS or T3 () was administered into the lateral ventricle. Depressive-like behaviors were induced by chronic restraint stress. The forced swimming (FST), tail suspension (TST), and open field (OFT) tests were used to investigate depression. The rats were sacrificed, and brain tissues were stored for molecular and pathological evaluations. Chronic stress increased the immobility of rats in the Model group according to FST, TST, and OFT (P < 0.05). T3 significantly improved depressive-like behaviors (P < 0.05). The gene expression and protein level of hippocampal NF-κB, NLRP3, ASC, and Caspase-1 significantly increased in the Model group compared to the control group (P < 0.05). The reduced hippocampal levels of NF-κB, NLRP3, ASC, and Caspase-1 were seen in the T3 group compared to the Model group (P < 0.05). Also, the Nissl staining of the CA1 region showed an increased number of dark neurons (P < 0.05) and reduced pyramidal layer thickness (P < 0.05) in the Model group. These histopathological alterations were changed by T3 administration compared to the Model group (P < 0.05). The findings of confirmed the therapeutic effects of intraventricularly T3 on depressive-like behaviors induced by restraint stress via surviving pyramidal neurons of the CA1 region and inhibition of NF-κB/NLRP3 inflammasome pathway.