Background: Traumatic brain injury (TBI) often leads to changes in body composition, including the loss of lean body mass, which increases the risk of adverse clinical outcomes such as infections, prolonged ICU stays, and higher mortality rates. These complications may be exacerbated if there is a deficiency of crucial micronutrients and macronutrients. Methods: This prospective observational study was performed in the Department of Neurosurgery, SMS Medical College, Jaipur, between July 2021 and March 2022. We recruited 200 TBI patients aged 15 to 80 years who had a post-resuscitation Glasgow Coma Scale (GCS) score of 3–8 (severe TBI). The “Malnutrition Universal Screening Tool” (MUST) was used to categorize nutritional status, while serum levels of electrolytes (sodium, potassium, calcium, phosphate, and vitamin B12) were measured. Data were collected at admission and at various intervals (24 hours, weekly) based on the study protocol. Statistical analysis was performed using SPSS 22.00. Results: Among the 200 participants, 68.5% were male. Age distribution showed that 62% were 31–45 years old, with a predominant etiology of road traffic accidents (69.5%). TBI severity categorization yielded mild in 26%, moderate in 30.5%, and severe in 43.5% of cases. Daily energy, protein, carbohydrate, and fat intake were significantly lower than recommended dietary allowances (p < 0.05). Macronutrient inadequacy for energy, protein, carbohydrates, and fiber was reported in 93.5%, 69%, 4.5%, and 71.5% of patients, respectively. Sodium levels were significantly associated with TBI severity, and mean calcium levels were lower in severe TBI cases, whereas potassium and phosphate showed no significant correlation with severity (p > 0.05). Conclusion: Identifying and correcting malnutrition (including both macroand micronutrient deficiencies) upon admission may reduce complications in TBI. Appropriate nutritional interventions, coupled with close monitoring of electrolytes, have the potential to improve outcomes in this population.