An important though uncommon complication of retained missiles is that of spontaneous migration. A 22 years young man presented to us with alleged firearm injury to head. The bullet migration was evident on the third day after injury when it was seen lying in the left posterior occipital region as compared to previous posterior frontal location. Softening of contused cerebrum along the missile tract and free weight of the bullet due to gravity were probably responsible for the bullet migration in this case. The patient underwent surgical exploration and progressively recovered. This case report emphasizes the fact that spontaneous migration of a foreign body in side the cranium should be watched for, resulting in damage to vital structures producing significant neurological damage. The presence of migration should be considered to be an urgent indication for surgical intervention.