The drama focuses on a group of people who travel to the Amazon to find a missing television explorer.
Deadline reports that Blackthorne has now signed up to play the producer of the explorer's series.
Blackthorne has appeared in a number of shows including ER, 24, Lipstick Jungle and The Gates. He recently had a guest role in White Collar.
The River also stars Bruce Greenwood, Joe Anderson and Eloise Mumford..