The Dolphins played without cornerbacks Sean Smith and Jason Allen, who were both sick. Also missing the game was linebacker Matt Roth, who has yet to practice this summer because of a controversial and much-discussed groin issue.
Hilliard gave the Dolphins the lead for good in the third quarter when he scored on a 39-yard touchdown run on his first carry of the game.
That touchdown came after a punt went off a Carolina player and was recovered by Dolphins rookie safety Chris Clemons at the Panthers 14-yard line.
Hilliard's 7-yard run on the next play helped the Dolphins move inside the 10-yard line.
Unlike the preseason opener against Jacksonville, the Dolphins used the Wildcat in this game.
The Dolphins ran five plays out of the formation in the first half, gaining 53 yards on those plays.
This one also should have resulted in a touchdown, but Pennington's pass to Cobbs was underthrown and Cobbs also had to wait for it, which allowed Panthers cornerback Chris Gamble to come back and tackle Cobbs at the Carolina 10-yard line.
The Dolphins failed to score a touchdown on the drive, settling for a 21-yard field goal by Connor Barth.
The Dolphins used their best offense to march 60 yards on six plays on their first drive to take a 7-0 lead.
Brown was the star of the drive with runs of 10 and 12 yards and then a 28-yard reception from Pennington down the right sideline for the touchdown.
The long Carolina return didn't produce any points after the Panthers threw an incomplete pass out of field goal formation on fourth down.
But Williams' fumble proved costly after it gave Carolina the ball at the Miami 29-yard line.
Six plays after the fumble, Decori Birmingham scored on a 2-yard run to give Carolina a 14-10 lead heading into halftime.
The Dolphins cut the lead to one on a 41-yard field goal by Dan Carpenter before Hilliard came up with his big play.