The worker was part of a team sent to lay electric cables in one of the reactors 13 days after the disaster.
He said in a 2012 interview that plant operator Tokyo Electric Power Co. should have known about the high radiation levels and warned them. He asked to be identified by only his first name, Shinichi, because of the social stigma of being labeled a troublemaker in Japan.
His exposure exceeded official limits, forcing him to stop working at the plant. It was not considered a serious health risk.
The lawsuit was filed Wednesday in Fukushima District Court.