We report the demonstration of a magneto‐optic sampling technique that allows for the detection of picosecond electrical pulses propagating down a microstrip transmission line. A unique feature of the method is that it directly measures the current in ultrashort electrical pulses. The technique is based on time‐resolved detection of the magneto‐optic Faraday effect in a Bi‐substituted yttrium‐iron‐garnet (Bi‐YIG) film. The detailed magnetic response is found to be in excellent agreement with the Bloch‐Bloembergen equations. The bandwidth of the sampling system has been demonstrated to scale with the ferromagnetic resonance frequency up to 82.3 GHz, with a potential for increase towards 1 THz.