Background: Accurate outcome prediction among patients with aneurysmal subarachnoid haemorrhage (aSAH) has remained elusive. We aimed to identify outcome predictors and develop a model to guide clinicians and the families of patients who are being considered for microsurgical repair of a ruptured aneurysm. Methods: We identified 246 consecutive patients with aSAH who underwent microsurgical clipping of the culprit aneurysm between 01/09/2011 and 20/07/2020. Independent predictors of outcome were identified using logistic regression and an outcome prediction model was developed. Results: Age>55 (OR3.35, 95%CI 1.06–10.56, p=0.04), high-grade aSAH (WFNS≥4) (OR7.82, 95%CI 2.66–22.98, p<0.001) and midline shift of ≥5mm (OR10.35, 95%CI 3.22–22.23, p<0.001) were all associated with unfavourable outcome (mRS≥4) at a mean of 87.27 (±53.40) days after ictus. Age>55 was also associated with inpatient mortality (OR4.98, 95%CI 1.83–13.54, p=0.002) and unfavourable outcome at final follow-up (OR3.76, 95%CI 1.26–11.20, p=0.002). Furthermore, midline shift of >5mm was significantly associated with inpatient mortality (OR5.55, 95%CI 1.74–17.64, p=0.004) and unfavourable outcome at final follow-up (OR9.71, 95%CI 3.25–29.04, p<0.001). Conclusions: Older age, poorer presenting WFNS grade and increased mass effect are all associated with poorer outcome among patients undergoing microsurgical clipping of a ruptured aneurysm. These data have been used to construct an outcome prediction model for these patients.