Injury severity is correlated with poor prognosis after traumatic brain injury (TBI). It is not known whether triglycerides (TGs) or total cholesterol (TC) is good biomarker of increased injury of neuroinflammation and apoptosis in a high fat diet (HFD)-treated rat after TBI episodes. Five-week-old male Sprague-Dawley (SD) rats were fed a HFD for 8weeks. The anesthetized male SD rats were divided into three sub-groups: sham-operated and TBI with 1.6atm or with 2.4atm fluid percussion injury (FPI). Cell infarction volume (triphenyltetrazolium chloride stain), tumor necrosis factor-alpha (TNF-α) expression in the microglia (OX42 marker) and astrocytes (Glial fibrillary acidic protein marker), TNF-α receptor expression in the neurons (TNFR1 and TNFR2 markers), and the extent of neuronal apoptosis (TUNEL marker) were evaluated by immunofluorescence, and the functional outcome was assessed by an inclined plane test. These tests were performed 72h after TBI. Serum triglyceride and cholesterol levels were measured at 24, 48 and 72h after TBI. The FPI with 2.4atm significantly increased body weight loss, infarction volume, neuronal apoptosis and TNF-α expression in the microglia and astrocytes, and it decreased the maximum grasp degree and TNFR1 and TNFR2 expression in neurons at the 3rd day following TBI. The serum TG level was positively correlated with FPI force, infarction volume, Neu-N-TUNEL, GFAP-TNFα, and OX42-TNFα Simultaneously; the serum TG level was negatively correlated with Neu-N-TNFR1 and Neu-N-TNFR2. TG is a good biomarker of increased injury for neuroinflammation and apoptosis at the 3rd day after TBI in HFD rats.