Subarachnoid hemorrhage (SAH) is a serious clinical condition where leakage of blood into the subarachnoid space causes an acute rise in intracranial pressure and reduces cerebral blood flow, which may lead to delayed cerebral ischemia and poor outcome. In experimental SAH, we have previously shown that the outcome can be significantly improved by early inhibition of the MAPK/ERK kinase/extracellular signal-regulated kinase (MEK/ERK1/2) pathway. The aim of this study was to apply mass spectrometry to investigate the overall late effects of experimental SAH on cerebrovascular protein expression. SAH was induced in rats that were treated with the MEK1/2 inhibitor U0126 or vehicle. Neurological outcome was assessed using a battery of behavioral tests. Specific protein expression of large cerebral arteries was analyzed quantitatively with high-throughput tandem mass spectrometry. SAH resulted in a marked reduction of neurological scores, which was counteracted by U0126 treatment. Mass spectrometry analysis demonstrated regulation of 184 proteins after SAH, regulations that were in part prevented by U0126 treatment. Network analysis identified several protein networks including a strong structural network centered around 14-3-3. Additionally, protein networks with functions in mRNA metabolism and protein folding were identified. Treatment with U0126 inhibited cerebral vessel wall pERK1/2 expression and significantly improved outcome of the rats. In conclusion, we show that SAH induces a broad array of specific changes in the overall protein networks in cerebral artery smooth muscle cells and suggest that this is essential for understanding the vascular pathophysiology after SAH.