Aneurysmal subarachnoid hemorrhage (SAH) is the extravasation of blood into the subarachnoid space and is fatal in most cases. Platinum coils have been used to fill the hemorrhage site and prevent the extravasation of blood. Here we explored the use of Pt-coated polymer nanofibers (NF) to prevent blood extravasation and were able to achieve improved results in vitro. The polymer nanofibers were produced via electrospinning and were subsequently electroplated with Pt, resulting in metalized nanofibers. These nanofibers were installed within a microfluidic channel, and the resulting reduction in the permeability was evaluated using a fluid similar to blood. Based on the obtained results, these newly developed nanofibers are expected to decrease the operation cost for SAH, owing to their reduced size and low material cost. Furthermore, it is expected that these nanofibers will be used in a smaller amount during SAH operation while having the same preventive effect. This should reduce the operational risk associated with the multiple steps required to place the Pt coils at the SAH site. Finally, the underlying hydrodynamic mechanism responsible for the reduced permeability of the synthesized nanofibers is described.