This paper presents a novel experimental method for impacting microscale single fibers under dynamic multiaxial loading conditions. Experimental setup is developed by modifying a 0.25-inch diameter Hopkinson bar to directly impact fibers. Using this setup, ultrahigh molecular weight polyethylene (UHMWPE) Dyneema® SK76 single fibers, with average diameter 17 µm, are transversely impacted with indenter radii of 200 (blunt), 20 (sharp), and 2 (razor) µm at velocities of 10 and 20 m/s, corresponding to nominal strain rates of 4000–6300 s−1. Compared to high strain rate (1156 s−1) uniaxial tensile loading, significant reductions in failure strains are measured for transverse impactwith blunt (34%), sharp (39%) and razor (61%) indenters. The reduction in tensile properties is attributed to strain rate and multiaxial stress-states induced byimpactor geometries; while all three geometries induced transverse compression, sharp and razor induced a greater degree of transverse shear,observed by failure surfaces.