This study investigated the role of fibrin on neutrophil extracellular traps (NETs) formation from neutrophils and to elucidate the involvement of mitochondria in NETs formation during periodontitis. Plasminogen-deficient (Plg-/-) mice were employed to evaluate the effects of fibrin deposition on inflammation, bone resorption, and neutrophil infiltration in periodontal tissues. In addition, invitro tests evaluated fibrin's impact on neutrophil-driven inflammation. Mitochondrial reactive oxygen species (mtROS) levels within neutrophils were quantified utilizing flow cytometry and immunofluorescence invitro. Furthermore, the anti-inflammatory properties of the mtROS scavenger, Mito-TEMPO, were confirmed to regulate the NET formation invitro and invivo. Plasminogen deficiency resulted in increased fibrin deposition, neutrophil infiltration, inflammatory factors concentration, and alveolar bone resorption in periodontal tissues. After neutrophils were treated by fibrin invitro, the expression of inflammatory factors, the formation of mtROS, and NETs enriched in mitochondrial DNA (mtDNA) were upregulated, which were reversed by Mito-TEMPO invitro. Moreover, Mito-TEMPO alleviated inflammation in Plg-/- mice. This study showed that fibrin deposition in gingiva induced the NET formation in Plg-/- mice, in which the DNA in NETs was from mitochondria depending on increasing mtROS.