O'Malley, the Democratic incumbent, got 56 percent of the vote compared to 42 percent for his Republican challenger.
O'Malley got little sleep before beginning Wednesday early going out to the streets of Baltimore with supporters waving signs thanking the voters for electing him to serve a second term.
Political coverage from NBC4.
Then he returned to the Maryland State House, where he received a warm welcome.
O'Malley entered to a standing ovation as he returned to work in Annapolis.
"I feel so blessed to be able to serve such a great state in these challenging times," he said. "We have a couple of hard years still ahead of us. But I know we're up to it, I know we really are."
Maryland's tax collector, Comptroller Peter Franchot, is hopeful the state can meet its challenges.
"Frankly, social progress but fiscal responsibility ... those two values are not at war with each other," he said.
Facing a billion dollar budget deficit, O'Malley said the state will have to live on a steady diet of cuts in spending, but he proposed no new taxes.
"My hope for the second term is that we come out of this miserable hard recession and that we come out of it before other states and that we make sure that these next two decades are decades when we make sure that Maryland is a winner in this new economy," he said.