The senate voted 27 to 20 to approve the increase.
It would increase the cost of a gallon of gas by about four cents this summer-and 13 to 20 cents a gallon in 2016.
The gas tax increase is expected to raise more than $4 billion over the next six years for transportation projects.
The Maryland House of Delegates already passed the bill.
Governor Martin O'Malley sponsored the bill and is expected to sign it into law.