In this letter we report experimental observations of transient UV‐induced frustration of the visible light transmission through Ge‐doped single mode fibers. Fiber side exposure to single nanosecond UV pulses at 266 and 248 nm is found to cause an abrupt decrease in transmission immediately following the pulse and a transmission recovery in microsecond time scale. Transmission changes were monitored at several visible wavelengths and for different types of Ge‐doped single mode fibers. The reported effect occurs independently of the growth and saturation of the permanent UV‐induced absorption reported by other authors. ©1995 American Institute of Physics.