The score came after Tannehill led the Dolphins on a 13-play drive following a missed 34-yard field-goal try by Atlanta's Matt Bryant with 4:46 to play.
The Miami quarterback passed for 236 yards (24-of-35) with one interception as the Dolphins (3-0) erased a pair of 10-point deficits and notched a third straight win to open the season for the first time since 2002.
Matt Ryan made good on 23-of-38 pass attempts for 231 yards and two touchdowns for the Falcons (2-1).
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