Patients with subarachnoid hemorrhage (SAH) who are using antiplatelet drugs prior to their hemorrhage, often receive platelet transfusions to reverse antiplatelet effects prior to life-saving surgical interventions. However, little is known about the effect of platelet transfusion on patient outcome in these patients. The aim of this study is to investigate the effect of platelet transfusion on clinical outcome in patients with aneurysmal SAH (aSAH) who use antiplatelet agents. Consecutive adult patients with an aSAH admitted between 2011 and 2015 to the Academic Medical Center (Amsterdam, the Netherlands) were included. Demographic characteristics and in-hospital complications were compared and clinical outcome was assessed after six months. Multivariable logistic regression analysis was performed to correct for confounding variables. A total of 364 patients with an aSAH were included. Thirty-eight (10%) patients underwent platelet transfusion during admission. Patients receiving platelet transfusion had worse clinical outcome (modified Rankin Scale score 4–6) at six months compared to patients without platelet transfusion (65% versus 32%, odds ratio 4.0, 95% confidence interval:1.9–8.1). Multivariable logistic regression analysis showed that platelet transfusion during admission was associated with unfavorable clinical outcome after six months; adjusted for age, treatment modality, modified Fisher and WFNS on admission (adjusted odds ratio 3.3, 95% confidence interval: 1.3–8.4). In this observational study, platelet transfusion was associated with poor clinical outcome at six months after correcting for confounding influences. In aSAH patients who need surgical treatment at low risk of bleeding, the indication for platelet transfusion needs careful weighing of the risk-benefit-balance.