Information on the effect of an intracerebroventricular (i.c.v.) injection of streptozotocin (STZ) on noncognitive behaviour in rodents such as depression states is scarce. Thus, the aim of this study was to examine the depressive-like effect of STZ injected by the i.c.v. route in mice and the potential protective effect of fluoxetine, antitumour necrosis factor-α (anti-TNF-α) and thalidomide. Our results indicated that a single injection of STZ (0.1 mg/site) promoted depressive-like behaviour in the tail suspension and sucrose preference tests without altering either locomotor activity or plasma glucose levels. We also showed that STZ increased TNF-α levels in the hippocampus of mice. Fluoxetine (32 mg/kg, intraperitoneally. 30 min before STZ injection), and the anti-TNF-α antibody (0.1 pg/site, i.c.v.) and thalidomide (3 mg/kg, subcutaneously), coadministered with STZ, prevented these effects. This is the first study to report depressive-like effects of STZ using the i.c.v. route in mice. We concluded that fluoxetine, anti-TNF-α antibody and thalidomide were effective in preventing depressive-like behaviour and the increase in TNF-α levels in the hippocampus of mice induced by an i.c.v. injection of STZ, reinforcing the involvement of TNF-α in the pathophysiology of depression. This model and the mechanisms studied may contribute towards the development of new antidepressant drugs and enhance the options for studying depression.