Purpose To evaluate functional outcomes of severe traumatic brain injuries after insertion of intracranial pressure (ICP) monitor at King Saud Medical City (KSMC) and their correlation to each other. Patients and Methods A retrospective observational study for all adult patients (age >18 years) who were diagnosed with severe head injury and underwent ICP insertion at KSMC. Patients diagnosed between 2017 and 2019 were included. Data for measured outcomes, Glasgow outcome scale (GOS), Karnofsky Performance Score (KPS) and length of stay (LOS) and prognostic factors, data like: age, gender and primary Glasgow coma score (GCS) was obtained from patients’ files and direct communication with patients or their caregivers. We also compared patients who underwent ICP monitoring alone with those who underwent ICP with decompressive craniectomy (DC). Follow-up period ranged from 6–24 months. Results Seventy-four patients were included in this cohort study. Outcome measurements for patients with decompression and ICP were lower than those with ICP alone. KPS and GOS showed strong correlation ( p <0.01) in whole cohort and in both subgroups (ICP alone and ICP with DC). KPS showed significant correlation with length of stay ( p =0.026). Conclusion ICP monitoring is valid tool in management of severely head injured patients. Patients who underwent DC had a worse outcome. KPS can be used as alternative tool to measure functional outcome in severe traumatic brain injury.