Exposure to high levels of fluoride in drinking water has been linked to cognitive impairment, but the molecular mechanisms underlying this neurotoxicity are not fully understood. In this study, a subchronic rat model was used to investigate whether fluoride-induced synaptic damage involves RhoA/ROCK pathway-mediated microglial activation and inflammation. The role of fasudil, a specific RhoA/ROCK inhibitor, was also evaluated. The results demonstrated that fluoride activated the RhoA/ROCK cascade, stimulated microglial activation and subsequent release of pro-inflammatory cytokines, and resulted in hippocampal synaptic injury. Conversely, fasudil attenuated these effects by downregulating Iba1, TNF-α, and ROCK2 expression. Taken together, these findings establish that RhoA/ROCK signaling critically mediates fluoride-induced neuroinflammation and synaptic damage, thereby offering a mechanistic basis for assessing the neurotoxic risk of environmental fluoride exposure.