Introduction: Diabetic ketoacidosis (DKA) is a common complication of type 1 diabetes mellitus (T1DM). Neurological complications of DKA are rare in adults. We report a case of young lady with T1DM who presented with severe DKA and complicated with subarachnoid hemorrhage (SAH). Case: A 19-year-old female was diagnosed with T1DM following an admission for DKA 2 months earlier. Her hemoglobin A1c was 17.2%, and autoimmune markers showed positive anti-glutamic acid decarboxylase (anti-GAD) antibodies (71 IU/mL) with negative anti-insulinoma-associated antigen 2 (anti-IA2) and islet cell antibodies. Her C-peptide level was low at 69 pmol/L. She was discharged with basal bolus insulin analogues, but she defaulted on her medications. She presented to the hospital 2 months later with a history of epigastric pain, vomiting, and breathlessness for 2 days, and was then found unconscious at home. There was no history of trauma. She was intubated for a poor Glasgow Coma Scale (E1V1M1). Blood results showed severe DKA with glucose 25 mmol/L, blood gas pH 6.572, bicarbonate 2.6 mmol/L, and ketone more than 8.8 mmol/L. She was started on insulin infusion and fluid resuscitation. DKA resolved after 24 hours. Computed tomography (CT) of the brain showed SAH in the right frontal and left frontotemporal regions. CT angiography of the brain reported no evidence of an intracranial aneurysm. She was extubated on day 4 of admission. Subsequent cerebral digital subtraction angiography was unremarkable. The patient achieved complete neurological recovery on follow-up. Conclusion This case highlights that severe DKA may rarely be associated with spontaneous SAH, which increases morbidity and mortality. Proposed mechanisms include vascular injury, oxidative stress from severe ketoacidosis, and endothelial dysfunction related to inflammatory mediators. Clinicians should have a high suspicion and consider neuroimaging in DKA patients with unexplained reduced consciousness or atypical neurological findings.