Peduncular hallucinosis is characterized by striking visual images, highly colored and mobile, which are recognized by the patient as imaginary. A 50-year-old-man underwent microvascular decompression for a classical right sided trigeminal neuralgia. During the procedure, the petrosal vein and a transverse pontine vein were sacrificed for trigeminal decompression. On the second postoperative day, the patient developed peduncular hallucinosis that disappeared on the forth postoperative day. This is the third case in the literature of peduncular hallucinosis after obliteration of veins of the petrosal venous complex for trigeminal neuralgia. The best policy in cerebellopontine angle surgery is to preserve the petrosal vein whenever possible to avoid complications related to venous congestion.