The Dolphins had taken a 13-10 lead earlier in the fourth quarter on a 47-yard field goal by Dan Carpenter after a couple of long completions from Matt Moore to Marlon Moore put them in field goal range.
The Dolphins actually missed great chances to build a bigger lead, first having to settle for a field goal after getting a first-and-goal at the 2 and then watching a safety be nullifed because of a penalty on Jason Taylor.
After the teams traded field goals in the second quarter, Tampa Bay tied the game in the final minute of the first half on an Earnest Graham touchdown run.
It came after Marshall fumbled near midfield.
The loss dropped the Dolphins to 2-1 in the preseason, heading into Thursday night's finale at home against Dallas.