But Dixon held his nerve and eased away to win his first race of the season.
"It was big," a delighted Dixon said. "It is nice to get that first win out of the way – we came up a little short in the last few races.
"I am super proud of this team. Honda has been working extremely hard to bounce back after last week [at Indianapolis].
"This is awesome – it is always good to be back in the winner's circle.
"Right now in the Indycar Verizon Series the competition is just so tough."
Ryan Hunter-Reay finished second while Alexander Rossi was third in a clean sweep of the podium positions for Honda.
The win was dominant - Dixon had plenty left in the tank, appeared to have the fastest car on both types of tyre and his team produced two flawless stops.
He moves up to second the championship standings - Rossi has taken the lead.
A second race on the Belle Isle street circuit awaits on Monday.