Objective: In 2015, a protocol to prevent rebleeding was implemented to improve the outcome of patients with ruptured intracranial aneurysm. We performed a single-center retrospective analysis to compare the outcomes of pre/post using protocol. Methodology: Over a 3-year period, 208 patients with ruptured cerebral aneurysm were treated at our institution. The protocol for preventing rebleeding was initiated in 2015. We compared the two cohorts between the group of patients before initiating the protocol ( n = 104) and after initiating the protocol ( n = 104). We analyzed the protocol for preventing rebleeding which consisted of absolute bed rest, adequate pain control, avoiding stimuli (R), keeping euvolemia (E), preoperative systolic blood pressure <160 mmHg and within 140–180 mmHg after definite treatment (S), a short course (<72 h) of intravenous transaminic acid, and aneurysm treatment as early as possible (T). Outcomes are presented as in-hospital rebleeding, delayed cerebral ischemia (DCI), and proportion of unfavorable outcomes (score of 4–6 on a modified Rankin scale at 6 and 12 months). Results: Postprotocol, there was a reduction in the incidence of in-hospital rebleeding from 6.7% to 2.8% ( P = 0.20, odds ratio [OR] = 0.4, 95% confidence interval [CI] = 0.10–1.63) and in the proportion of patients who presented with good WFNS grades (1–3) with unfavorable clinical outcomes at 12 months from 27.0% to 12.8% ( P = 0.03, OR = 0.40, 95% CI = 0.17–0.95). The DCI experienced a significant reduction from 44.2% to 7.7% ( P < 0.001, OR = 0.10, 95% CI = 0.04–0.23), and their 180-day mortality rate in good WFNS grades patients decreased from 16.3% to 8.8% (hazard ratio 0.80, 95% CI = 0.28–2.28). Conclusion: Ruptured cerebral aneurysm patients benefit from this protocol due to its ability to reduce the incidence of DCI and reduce unfavorable outcome on good WFNS grade patients.