Batson, 26, had 22 catches for 197 yards with two touchdowns in three seasons with Tennessee, including two with Smith as tight ends coach and offensive coordinator. Batson started three games.
The Falcons announced the signing on Thursday.
Batson's first catch in 2018 came on a pass from Mariota, who is preparing for his first season with Atlanta.
Batson suffered a season-ending right knee injury last season, when he had only two catches for 15 yards, including one for a touchdown, in four games. He could also compete for a spot as a return specialist after returning 16 kickoffs with Tennessee.
Batson joins a long list of newcomers at wide receiver for Atlanta, beginning with first-round draft pick Drake London and also including veterans Bryan Edwards, Auden Tate, Damiere Byrd and KhaDarel Hodge, among others.
The Falcons released offensive lineman Rashaad Coward in a corresponding move.
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