Background Metabolic and inflammation dysregulation are important mechanisms in neurodegenerative diseases, but their study in behavioral variant frontotemporal dementia (bvFTD) is very scarce; we aimed to investigate the separate and interactive effects of metabolic and inflammatory dysregulation on central degeneration and cognitive function in patients with bvFTD. Methods This study recruited participants with bvFTD and healthy controls (HC) from December 15, 2017, to September 5, 2024, in the Department of Neurology of Xuanwu Hospital, underwent assessment of plasma targeted metabolite, plasma inflammatory factors, 18F-fludeoxyglucose-positron emission tomography/magnetic resonance imaging, and neuropsychological assessments. Linear regression models and interaction models were implemented using age, sex and education level as covariates to explore the association between differential metabolites and peripheral inflammatory markers with neuroimaging, and clinical measures. Results Forty bvFTD patients and 40 HC (56.25% female, mean age of 63.55 years) were involved. A total of 36 plasma differential metabolites were screened out with variable importance in projection (VIP) > 1 and p < 0.05. Differential metabolites distributed in metabolic pathways that regulate inflammation, such as Aminoacyl-tRNA biosynthesis, mTOR signaling and amino acid metabolism. Furthermore, differential metabolites and plasma inflammatory factors are correlated with atrophy and glucose metabolism in certain frontal-temporal brain regions, as well as cognitive function (p < 0.05). Additionally, the interaction between differential metabolites and inflammatory factors is associated with atrophy and glucose metabolism in the entire frontal-temporal brain region, as well as cognitive function (p < 0.05). Under conditions of dysregulation of inflammatory factors such as Interleukin, Interferons, and Tumour necrosis factor, metabolites in Aminoacyl-tRNA biosynthesis, mTOR signaling, and amino acid metabolism have a more pronounced impact on frontotemporal lobar degeneration and cognitive symptoms (p < 0.05). Conclusions This study shows that bvFTD exhibits peripheral metabolic and inflammatory dysregulation, which are associated with frontotemporal lobar degeneration and clinical symptoms, and the interaction effects of metabolic and inflammatory dysregulation have a greater impact on bvFTD.