Baldwin struggled during his two seasons in Kansas City after being selecting 26th overall in 2011, never seeming comfortable in offensive schemes under Bill Muir and Brian Daboll.
He hauled in 41 passes for 579 yards and two touchdowns in 26 games, but received criticism for consistently dropping balls.
The former Pitt Panther was one of the last picks for former Chiefs General Manager Scott Pioli.
“We felt like this trade was beneficial for all parties involved,” current General Manager John Dorsey said. “A.J. is a talented individual with a skillset that we feel can add value to our football team. Jon Baldwin is a hardworking player and a professional. We wish him nothing but the best moving forward.”
Jenkins played in three games for San Francisco last season after being taken 30th overall in the 2012 draft.