Marshall coach Doc Holliday announced Smith's transfer Thursday.
A senior, Smith left the Nittany Lions in June due to personal reasons. He is eligible to play this season.
Smith is the second former Nittany Lions player to transfer to Marshall, joining junior cornerback Derrick Thomas.
Smith started last season for the Nittany Lions and recorded 25 receptions for 402 yards, ranking third on the team in both categories. He was projected as a starter on Penn State's depth chart released after spring practice, although he missed much of the spring with a foot injury.
It's unclear if Smith's exit at Penn State was related to a charge for possession of a small amount of marijuana and drug paraphernalia. The charges stem from a March 14 incident where police searched Smith's apartment. Smith has applied for the Accelerated Rehabilitative Disposition program.
Information from ESPN.com Big Ten blogger Adam Rittenberg and The Associated Press was used in this report.