The worker, who was a civil contractor, died Tuesday while excavating a trench at the mine.
An investigation has been launched by local authorities.
"Our sincere condolences go out to the family of the contractor and the community during this difficult time," said Alex Black, president and CEO at Rio Alto.
In September 2011, operations at the mine were stopped following a workers' strike.
The La Arena gold and copper project is Rio Alto's primary operation but the company holds several other exploration properties in Latin America.